A method, apparatus, and storage medium for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations.

Abstract

This invention discloses a method, apparatus, and storage medium for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations, belonging to the field of computational simulation and design of nanomaterials. First, this invention constructs modified carbon nanotube models for different active grafting sites or different types of functional grafted functional groups in the initial carbon nanotube model, and performs geometric optimization to obtain stable configurations. Then, it calculates the microstructure and electronic properties of the stable configurations. Next, it selects the stable configuration from the previous step, constructs grafted single-walled carbon nanotube models with different doping gradients, and performs geometric optimization to obtain stable configurations. Then, it calculates the energy levels and binding density of states based on the optimized stable configurations with different doping levels. Finally, it evaluates the structure and properties of the surface-modified carbon nanotubes. This invention studies the structural changes and performance improvements brought about by functional group grafting to carbon nanotubes, avoiding the costs associated with experiments and mitigating many uncertainties in experiments.

Description

Technical Field

[0001] This invention belongs to the field of computational simulation and design of nanomaterials, and specifically relates to a method, device and storage medium for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations. Background Technology

[0002] Carbon nanotubes, with their excellent mechanical, electrical, and chemical properties, have shown broad application prospects in various fields such as nanoelectronic devices and composite materials. However, their inherent chemical inertness and strong inter-tube van der Waals forces have limited their functionalization development and high-performance application range. Surface functional group modification technology, which involves grafting various functional groups onto the surface of carbon nanotubes using chemical methods, has become one of the effective ways to regulate their properties, optimize their dispersion ability, and improve their interfacial interactions with other materials.

[0003] Traditional experimental methods can clarify the regulatory effect and improvement law of functional group grafting on the macroscopic properties of carbon nanotubes through a series of tests and characterization methods. However, due to the limitations of technical means, it is difficult to accurately analyze the bonding type, charge transfer law and orbital hybridization characteristics of functional groups and carbon nanotube surfaces. This kind of microstructure information is the core factor that determines the stability of functional group grafting, the evolution of the electronic structure of carbon nanotubes, and thus dominates the changes in their macroscopic properties.

[0004] Meanwhile, the carbon nanotubes used in traditional experimental studies are mostly mixed chiral systems, and the functional group grafting sites, grafting orientation and other influencing factors such as the chirality of carbon nanotubes are coupled with each other, making it difficult to achieve precise control of a single variable. Therefore, it is impossible to independently explore the specific contribution of a certain factor to the modification effect of carbon nanotubes.

[0005] This invention constructs an idealized research model through first-principles calculations, accurately analyzes its microscopic mechanism of action, and freely controls various influencing variables. It accurately predicts various key performance indicators of functional group-grafted carbon nanotube systems, which can provide theoretical support for the high-performance application of single chiral functionalized carbon nanotubes, and also conduct forward-looking research on the directional design of its composite materials. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method based on first-principles calculations grounded in quantum mechanics, which can directly output key microscopic data such as binding energy, charge population, and density of states during the functional group grafting process. This not only clarifies the thermodynamic feasibility of functional group grafting but also precisely analyzes its microscopic mechanism of action. This provides a solid theoretical basis for fundamentally explaining the mechanism by which functional group modification regulates the performance of carbon nanotubes and also provides theoretical support for the high-performance application of single-chiral functionalized carbon nanotubes.

[0007] This invention provides a method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations, comprising the following steps:

[0008] Step 1: Construct an initial carbon nanotube model and a functional group model; graft functional groups onto the surface of carbon nanotubes through covalent bonding; construct modified carbon nanotube models for different active grafting sites or different types of functional grafted functional groups in the initial carbon nanotube model.

[0009] Step 2: Perform geometry optimization on the modified carbon nanotube model to obtain a stable configuration that satisfies energy convergence;

[0010] Step 3: Based on the optimized modified carbon nanotube model, the microstructure and electronic properties of modified carbon nanotubes with different active grafting sites or different types of functional grafting functional groups are calculated using first-principles calculations.

[0011] Step 4: Select the stable configuration from Step 2, and construct grafted single-walled carbon nanotube models with different doping gradients by adjusting the doping ratio of functional groups and perform geometric optimization to obtain stable configurations with corresponding doping amounts that satisfy energy convergence.

[0012] Step 5: Based on the optimized modified carbon nanotube models with different doping gradients, first-principles calculations are used to calculate energy levels and density of states, and to evaluate the chemical reactivity and high carrier mobility modification strategies of modified carbon nanotubes with different doping amounts.

[0013] Step 6: Evaluate the structure and properties of surface-modified carbon nanotubes based on the parameters calculated in Steps 3 and 5.

[0014] Furthermore, in step 1, the initial carbon nanotube model is an aperiodic single-walled carbon nanotube model, and the dangling bonds at both ends of the single-walled carbon nanotube model are saturated with H atoms.

[0015] Furthermore, in step 1, the functional group is an organic functional group; the grafting sites of the functional group are located in the tube and at both ends of the initial carbon nanotube model.

[0016] Furthermore, the organic functional group includes one or more of hydroxyl, carboxyl, amino, ester, and amide groups.

[0017] Furthermore, in step 2, the DMol3 module of MS software was used to perform geometric optimization on modified carbon nanotube models with different grafting sites or different grafted functional groups. During the calculation, GGA-PBE functionals were used for all-electronic structure calculations, and the basis set was selected as the DNP numerical basis set containing polarization functions. Dispersion correction was used to handle weak interactions between functional groups. The convergence criterion for geometric optimization was: with fine precision, the system energy convergence criterion was 10e-5 Ha, force convergence tolerance is 0.002 Ha / Å, atomic displacement convergence standard is 0.005 Å, and the remaining parameters are the default parameters under Fine precision.

[0018] Furthermore, the microstructure and electronic properties of the modified carbon nanotubes include bond length, binding energy, electrostatic potential, dipole moment, energy level, and density of states.

[0019] Furthermore, the doping amount is the ratio of the number of carbon atoms in the functional group to the number of atoms in the carbon nanotube.

[0020] Further, in step 4, the DMol3 module of MS software was used to perform geometric optimization on modified carbon nanotube models with different grafting sites or different grafted functional groups. During the calculation, GGA-PBE functionals were used for all-electronic structure calculations, and the DNP numerical basis set containing polarization functions was selected. Dispersion correction was used to handle weak interactions between functional groups. The model was calculated using the option of unrestricted selection and the use of symmetry, and temperature broadening was enabled. The convergence criterion for geometric optimization was: with fine precision, the system energy convergence criterion was 10e -5 Ha, force convergence tolerance is 0.002 Ha / Å, atomic displacement convergence standard is 0.005 Å, and the remaining parameters are the default parameters under Fine precision.

[0021] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations as described above.

[0022] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations as described above.

[0023] The present invention also provides a computer program product, including a computer program / instructions, which, when executed by a processor, implements the steps of the method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations as described above.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention, based on materials simulation, efficiently and accurately obtains the changes in the intrinsic structure of carbon nanotubes brought about by functional groups. Through in-depth mechanistic research, it deeply investigates the structural changes and performance improvements of carbon nanotubes brought about by different active grafting sites or different types of functional grafting groups. Furthermore, by using H-atom saturation of dangling bonds at the ends of carbon nanotubes, the model is made more closely aligned with the experimental environment. In addition to the grafting sites and functional groups, this invention can further explore the influence of doping concentration. This method provides a theoretical basis for the high-performance application of single-chiral carbon nanotubes while offering a precise implementation plan for the screening and reverse design of new materials. It ensures the accuracy of the quantum-level mechanism revelation and directly provides practical strategies for experimental modification, significantly reducing trial-and-error costs. Attached Figure Description

[0026] Figure 1 This invention is based on a first-principles calculation flowchart;

[0027] Figure 2 Molecular models of functional groups grafted onto carbon nanotubes at different sites; wherein, (a) the initial carbon nanotube, (b) the tube grafted with hydroxyl groups, (c) the tube grafted with carboxyl groups, (d) the tube grafted with amino groups, (e) the end grafted with hydroxyl groups, (f) the end grafted with carboxyl groups, and (g) the end grafted with amino groups.

[0028] Figure 3 A magnified view of a pure carbon nanotube and the atomic numbers near the grafting sites;

[0029] Figure 4 Electrostatic potential of functional groups grafted in tubes; (a) initial carbon nanotubes, (b) tubes grafted with hydroxyl groups, (c) tubes grafted with carboxyl groups, (d) tubes grafted with amino groups.

[0030] Figure 5 Electrostatic potential of terminal grafted functional groups; (a) terminal grafted hydroxyl group, (b) terminal grafted carboxyl group, (c) terminal grafted amino group;

[0031] Figure 6 Frontier molecular orbitals of functionalized carbon nanotubes grafted with tubes; (a) HOMO and LUMO orbitals of the initial carbon nanotube, (b) HOMO and LUMO orbitals of hydroxyl groups grafted with tubes, (c) HOMO and LUMO orbitals of carboxyl groups grafted with tubes, (d) HOMO and LUMO orbitals of amino groups grafted with tubes.

[0032] Figure 7 Frontier molecular orbitals of end-grafted functional group carbon nanotubes; (a) HOMO and LUMO orbitals of end-grafted hydroxyl groups, (b) HOMO and LUMO orbitals of end-grafted carboxyl groups, (c) HOMO and LUMO orbitals of end-grafted amino groups.

[0033] Figure 8 Frontier molecular orbital energy level diagrams of carbon nanotubes with different grafting types;

[0034] Figure 9 Density of states of carbon nanotubes under different grafting types;

[0035] Figure 10 Models of carbon nanotubes modified with different carboxyl doping amounts; (a) 1% COOH, (b) 3% COOH, (c) 5% COOH, (d) 7% COOH, (e) 10% COOH, (f) 11% COOH;

[0036] Figure 11 Frontier molecular orbital energy level diagrams of modified carbon nanotubes with different doping concentrations;

[0037] Figure 12 Density of states of modified carbon nanotubes with different doping amounts. Detailed Implementation

[0038] The present invention will now be further described with reference to the accompanying drawings.

[0039] This invention is based on first-principles calculations and uses density functional theory as the computational method to perform surface grafting treatment on carbon nanotubes, selecting organic functional groups. After structural optimization, a series of structural and property calculations are performed, including adsorption energy, electrostatic potential, leading molecular orbitals, dipole moments, and density of states. By changing the type and site of grafting and the amount of doping, this invention explores the influence of the introduction of functional groups on the intrinsic structure of carbon nanotubes, while simultaneously improving the chemical activity and electrical conductivity of carbon nanotubes.

[0040] This invention includes the following steps:

[0041] Step 1: Model carbon nanotubes and multiple functional groups using Materials Studio software;

[0042] Functional groups are grafted onto the surface of carbon nanotubes via covalent bonding, with the main grafting sites being the middle and end of the carbon nanotubes.

[0043] The DMol3 module was used to perform geometric optimization on each modified carbon nanotube model. After the geometric optimization was completed and all convergence parameters met the convergence criteria, the bond lengths of C atoms near the functional group grafting sites were recorded to ensure the rationality of the model and the accuracy of subsequent calculation results.

[0044] Calculations were performed on carbon nanotubes grafted with different functional groups and at different grafting sites, including bond length, binding energy, electrostatic potential, molecular polarity, and frontier molecular orbitals, and the energy levels of each carbon nanotube were also calculated.

[0045] Step 2: Based on the calculations in Step 1, the simulated structures and properties of various carbon nanotubes are fully compared to screen for grafting groups and grafting sites with high chemical reactivity and carrier mobility, and the doping amount is further changed.

[0046] Model modified carbon nanotubes with different doping levels, and fully optimize the model structure to reduce the energy to a stable configuration;

[0047] Frontier molecular orbitals and energy levels of carbon nanotubes with different doping amounts were calculated, and modification strategies with high chemical reactivity and high carrier mobility were formulated in combination with density of states.

[0048] A preferred embodiment of the present invention includes:

[0049] Bond length refers to the structural changes between the C atom at the grafting site and other C atoms in the carbon nanotube, as well as the changes in C-C bond length, which affect the carbon nanotube before and after modification.

[0050] Binding energy refers to the energy released or required when particles (such as atoms, molecules, or nucleons) come together. The specific calculation formula is as follows:

[0051]

[0052] In the formula E A and E B E represents the energy possessed by the optimized functional group and the pure carbon nanotube, respectively. A+B The energy of the grafted system can be represented by the difference between the individual calculations to obtain the binding energy E of the functional group-grafted carbon nanotubes. int The smaller the value, the more stable the system;

[0053] In the field of quantum chemical calculations, electrostatic potential is often used to calculate and analyze the interactions between molecules. It can be used to characterize the stacking structure and arrangement of molecules. Its contribution comes from two parts: nuclear charge and extranuclear electrons. The warm color region represents the positive region of electrostatic potential, and the cold color region represents the negative region of electrostatic potential.

[0054] The dipole moment is the product of the distance between the centers of positive and negative charges and the amount of charge. It is a vector quantity, directed from the center of positive charge to the center of negative charge, and is usually represented by the symbol μ. It reflects the polarity of a molecule or system.

[0055] Frontier molecular orbital (FMO) calculations can effectively analyze the electron cloud arrangement characteristics and conjugation behavior in molecules. They mainly include calculating the lowest unoccupied orbital (LUMO) and the highest occupied orbital (HOMO) in molecular orbitals.

[0056] The energy between the LUMO and HOMO orbitals of a molecule is called the "band gap," also known as the "HOMO-LUMO energy level" of the molecule.

[0057] The magnitude of an energy level measures how easily a molecule can be excited; a large energy level indicates that the molecule is difficult to excite, while a small energy level indicates that the molecule is easy to excite. Furthermore, it can be used to infer the chemical reactivity of various grafting types.

[0058] Density (DOS) can directly reflect the charge carrier transport capability of a material, which plays a key role in the study of the optoelectronic properties of materials.

[0059] According to the variable-range jump conductivity described in Mott's theory:

[0060]

[0061]

[0062]

[0063] In the formula, ρ is a dimensionless constant (≈18.1), N(E) is the density of states of the material at the Fermi level, α is the inverse velocity at the wave function, e is the electron charge, ν is the jump rate factor, and k B It is the Boltzmann constant, and the transition distance r can be obtained from the equation:

[0064]

[0065] The relationship between σ and N(E) at a specified temperature:

[0066]

[0067] Electrical conductivity is a physical parameter describing the ease with which charge transport occurs in a material. The relationship between electrical conductivity and carrier mobility in a material is as follows:

[0068]

[0069] In the formula, n and μ n This represents the concentration and mobility of electrons; p and μ p This refers to the concentration and mobility of holes. By calculating the density of states near the Fermi level of carbon nanotubes with different grafting types, we can evaluate their carrier mobility.

[0070] Example 1

[0071] In this embodiment, a (6,6) armchair-shaped single-walled carbon nanotube is used as an example, and hydroxyl, carboxyl and amino functional groups are grafted onto it respectively.

[0072] Step 1: Model (6,6) armchair-shaped single-walled carbon nanotubes using Materials Studio software. To better simulate the experimental environment, dangling bonds at both ends of the carbon nanotubes are saturated with H atoms.

[0073] Modeling three functional groups—hydroxyl, carboxyl, and amino—is used. These functional groups are introduced into single-walled carbon nanotubes using two grafting methods: in-tube and end-cap grafting, to construct models of surface-modified carbon nanotubes, such as... Figure 2 As shown;

[0074] The naming conventions for carbon nanotubes modified in various ways are as follows: pure carbon nanotubes are denoted as CNT; hydroxyl, carboxyl, and amino groups grafted into the tube are denoted as CNT-OH(M), CNT-COOH(M), and CNT-NH2(M), respectively; hydroxyl, carboxyl, and amino groups grafted at the ends are denoted as CNT-OH(E), CNT-COOH(E), and CNT-NH2(E), respectively.

[0075] Step 2: Use the DMol3 module of MS software to perform geometric optimization on each model, with the algorithm set to GGA-PBE; use the polarization function (DNP) for all-electron calculations;

[0076] Considering the possible weak interactions between functional groups, a dispersion force correction based on density functional theory is adopted, and the model is calculated using the option of unrestricted selection and the use of symmetry, with temperature broadening enabled.

[0077] During the geometry optimization process, the relevant accuracy is performed with fine precision, where the convergence criteria for energy, force, and displacement are set to 10e. -5 Ha, 0.002 Ha / Å and 0.005 Å;

[0078] Step 3: Evaluate the properties of grafted (6,6) armchair-shaped single-walled carbon nanotubes

[0079] (1) Through geometric optimization, for the grafted functional groups in the tube, the C atoms at the grafting site protrude outward from the tube compared to the C atoms at other positions in the carbon nanotube. Figure 3 As shown in the figure, the C atom of the directly grafted group is denoted as C0, and the three surrounding carbon atoms are denoted as C1, C2 and C3, respectively.

[0080] The grafting of functional groups increases the C-C bond length near the grafting site. This is because the C atoms on the surface of the carbon nanotubes bond through sp... 2 The hybridization site fully bonds with the surrounding three C atoms, forming conjugated π bonds on the surface. When carbon nanotubes are hydroxylated, the -OH group is extruded from the carbon nanotube. The binding force of the OC bond causes the C atom to protrude outward, thus causing a change in the length of the three C-C bonds associated with the C atom connected to the hydroxyl group. The hybridization of the C atom located at the -OH functionalization site changes, resulting in local sp. 3Hybridization disrupts the conjugated π bonds on the CNT surface, making it more susceptible to interaction with other substances. The same principle applies when grafting carboxyl and amino groups.

[0081] Table 1 Bond Length Parameters

[0082]

[0083] (2) The binding energy of the modified carbon nanotubes was obtained by calculating the energy of the pure carbon nanotubes and the optimized energy of each group and each grafting site.

[0084] Table 2 Binding energy of single carbon nanotubes with different grafting types and grafting sites

[0085]

[0086] When grafting in a tube, E int A value <0 indicates that grafting groups in the tube is thermodynamically favorable. Compared to end grafting, which requires external energy to occur, in-tube grafting can proceed spontaneously. Furthermore, the binding energy is lowest when grafting hydroxyl groups into the tube, resulting in a more stable configuration compared to grafting carboxyl and amino groups into the tube.

[0087] (3) In Figure 4 In the electrostatic potential calculation of the functional group-grafted carbon nanotubes shown, it was found that for hydroxyl grafting, the area around the H atom in -OH exhibits a positive value region, while the area around the O atom shows a more obvious negative value region, which disrupts the original uniform distribution of electrons.

[0088] The electrostatic potential results of grafting carboxyl and amino groups into the tube also changed compared to the original carbon nanotubes; the positive values ​​around the H atoms of the carboxyl group were darker, and the negative values ​​around the O atoms were darker, while the negative regions appeared around the N atoms when amino groups were grafted. After grafting functional groups, the electrostatic potential distribution of the original carbon nanotubes changed, and the darker color of the positive regions represented an increase in the polarizability of the material, which may be related to electron migration in the material;

[0089] Similar to grafting in tubes, hydroxyl groups are grafted at the ends, and the positive color near the grafting site H becomes darker, as shown in the following results. Figure 5 As shown, a lighter-colored negative potential region appears around the hydroxyl O atom. After carboxyl grafting, the positive potential around the H atom of the carboxyl group is more pronounced, and a significant negative potential appears near the O atom, resulting in a significant change in the uniform distribution of electrostatic potential compared to the original carbon nanotube. The electrostatic potential distribution of the amino group grafted at the end is similar to that of the hydroxyl group. This further illustrates that the introduction of functional groups disrupts the electrostatic potential distribution of carbon nanotubes, which will enhance the carrier transport capability of carbon nanotubes.

[0090] (4) The following data can be obtained from the calculation of the dipole moment;

[0091] Table 3. Dipole moments of different grafting types

[0092]

[0093] Unmodified pure carbon nanotubes are nonpolar molecules. When hydroxyl, carboxyl, and amino groups are introduced, their dipole moments increase, transforming them into polar molecules. This increases their solubility in polar solvents and makes them more compatible with polar molecules. When functional groups are grafted onto the tubes, hydroxyl grafting has the greatest effect on increasing the polarity of carbon nanotubes. However, when amino groups are used to replace the H atoms at the ends of the grafts, the effect on the polarity of carbon nanotubes is the greatest compared to the other two types of end-grafting.

[0094] (5) Calculations using frontier molecular orbitals (FMOs) Figure 6 , Figure 7 It can be observed that after grafting hydroxyl groups into the tube, the distribution of electron cloud exhibits a directional pattern. HOMO and LUMO tend to attach near the grafting site of the functional group, while the electron cloud distribution on the tube wall opposite the grafting site is significantly reduced. Furthermore, when carboxyl and amino groups are introduced, the electron cloud distribution of carbon nanotubes also exhibits a directional pattern, similar to that of hydroxyl grafting, with a tendency to concentrate near the grafting site of the functional group.

[0095] In nucleophiles, we should consider the localization of the HOMO orbital, as electrons from this orbital participate in the reaction more freely. Similarly, frontier orbital theory predicts that the lowest unoccupied orbital localization site is a favorable electrophilic site.

[0096] When the functional group replaces the H at the end of the carbon nanotube, the electron cloud distribution of the carbon nanotube does not exhibit the particularly obvious directionality that exists when grafting is done in the tube.

[0097] An energy level diagram was drawn using the calculated orbital energy levels, and the results are as follows: Figure 8 As shown, compared to grafting functional groups at the ends of carbon nanotubes, grafting within the tube results in higher chemical reactivity. This is because introducing functional groups into the tube disrupts the conjugated π bonds on the CNT surface, making it more susceptible to interaction with other substances. CNT-COOH(M) exhibits the most significant activation effect. Furthermore, since the energy level of CNT-COOH(M) is 0.486 eV, the lowest among various grafting types, it also demonstrates excellent carrier transport capabilities.

[0098] (6) Further calculations of the density of states near the Fermi level for carbon nanotubes with different grafting types can be used to evaluate their carrier mobility. Figure 9 );

[0099] Figure 9The dashed line at zero energy corresponds to the Fermi level of carbon nanotubes. Different grafted carbon nanotubes exhibit different densities of states at the Fermi level. When functional groups are grafted at the ends, the difference in density of states is not significant. However, when carboxyl groups are grafted in the tube, the density of states at the Fermi level of carbon nanotubes is the largest, indicating that the carrier migration ability of carbon nanotubes is the strongest at this time.

[0100] By introducing functional groups, the polarity and chemical reactivity of carbon nanotubes have been improved to a certain extent. In the next step, we will graft carboxyl groups into the tubes with the highest carrier migration ability and further adjust the doping amount of carboxyl groups for relevant calculations.

[0101] Step 4: Evaluate the properties of grafted (6,6) armchair-shaped single-walled carbon nanotubes by varying the doping amount.

[0102] The doping amount is defined as the ratio of the number of C atoms in the group to the number of carbon atoms in the carbon nanotube. The carboxyl doping amounts were adjusted to 1%, 3%, 5%, 7%, 10%, and 11%, and models of surface-modified carbon nanotubes with different doping amounts were constructed sequentially. The models are shown below. Figure 10 As shown;

[0103] Geometric optimization was employed to bring all parameters to convergence. The optimized parameters were: all-electronic structure calculations were performed using GGA-PBE functionals; the basis set was a DNP numerical basis set containing polarization functions; and dispersion corrections were used to handle weak interactions between functional groups. With fine precision, the system energy convergence criterion was 10e⁻¹. -5 Ha, the force convergence tolerance is 0.002 Ha / Å, and the atomic displacement convergence standard is 0.005 Å.

[0104] After ensuring the model achieves a reasonable and stable configuration, the band gap of each model is calculated:

[0105] exist Figure 11 As shown in the energy level diagrams for different doping levels, when the carboxyl group doping level is 10%, the energy level has the minimum value and the highest chemical reactivity, making its surface more likely to interact with other substances and greatly improving the dispersibility of carbon nanotubes in other materials.

[0106] Density of binding states ( Figure 12 It can also be seen that when the doping amount is 10%, the electronic density of states at the Fermi level is the largest, showing the strongest carrier transport capability.

[0107] In summary, the above embodiments are based on first-principles calculations and employ density functional theory. By constructing models and performing geometric optimization, reasonable and stable carbon nanotube models with different functional groups and grafting sites are obtained. Subsequently, through calculations of binding energy, electrostatic potential, molecular polarity, frontier molecular orbitals, and density of states, the influence of functional groups on the intrinsic structure of carbon nanotubes is explored. At the same time, functional groups and modification strategies that can bring higher chemical activity and electrical conductivity are screened out. Then, by further adjusting the doping amount, the most favorable modification strategy is determined using energy levels and density of states as indicators.

[0108] This approach overcomes the waste of manpower and resources associated with traditional experimental methods, reduces trial-and-error costs, and saves time and resources through a convenient and quick method, providing a solid theoretical foundation for the high-performance application of single-chiral carbon nanotubes.

[0109] In particular, in some preferred embodiments of the present invention, a computer device is also provided, including a memory and a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations as described in any of the above embodiments.

[0110] In some other preferred embodiments of the present invention, a computer-readable storage medium is also provided, on which a computer program / instruction is stored, wherein when the computer program is executed by a processor, the steps of the method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations as described in any of the above embodiments are implemented.

[0111] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above embodiments of the method for evaluating the structure and properties of surface-modified carbon nanotubes based on first principles, which will not be repeated here.

Claims

1. A method for evaluating the structure and properties of surface-modified carbon nanotubes based on first-principles calculations, characterized in that, Includes the following steps: Step 1: Construct an initial carbon nanotube model and a functional group model; graft functional groups onto the surface of carbon nanotubes through covalent bonding; construct modified carbon nanotube models for different active grafting sites or different types of functional grafted functional groups in the initial carbon nanotube model. Step 2: Perform geometry optimization on the modified carbon nanotube model to obtain a stable configuration that satisfies energy convergence; Step 3: Based on the optimized modified carbon nanotube model, the microstructure and electronic properties of modified carbon nanotubes with different active grafting sites or different types of functional grafting functional groups are calculated using first-principles calculations. Step 4: Select the stable configuration from Step 2, construct modified carbon nanotube models with different doping gradients by adjusting the doping ratio of functional groups, and perform geometric optimization to obtain stable configurations with corresponding doping amounts that satisfy energy convergence. Step 5: Based on the optimized modified carbon nanotube models with different doping gradients, first-principles calculations are used to calculate energy levels and density of states, and to evaluate the chemical reactivity and high carrier mobility modification strategies of modified carbon nanotubes with different doping amounts. Step 6: Evaluate the structure and properties of surface-modified carbon nanotubes based on the parameters calculated in Steps 3 and 5.

2. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 1, characterized in that, In step 1, the initial carbon nanotube model is an aperiodic single-walled carbon nanotube model, and the dangling bonds at both ends of the single-walled carbon nanotube model are saturated with H atoms.

3. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 1, characterized in that, In step 1, the functional group is an organic functional group; the grafting sites of the functional group are located in the tube and at both ends of the initial carbon nanotube model.

4. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 3, characterized in that, The organic functional group includes one or more of hydroxyl, carboxyl, amino, ester, and amide groups.

5. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 1, characterized in that, In step 2, the DMol3 module of MS software was used to perform geometric optimization on modified carbon nanotube models with different grafting sites or different grafted functional groups. During the calculation, GGA-PBE functionals were used for all-electronic structure calculations, and the DNP numerical basis set with polarization functions was selected. Dispersion correction was used to handle weak interactions between functional groups. The model was set to be unrestricted and symmetry was used for calculation, and temperature broadening was enabled. The convergence criterion for geometric optimization was: with fine accuracy, the system energy convergence criterion was 10e -5 Ha, force convergence tolerance is 0.002 Ha / Å, atomic displacement convergence standard is 0.005 Å, and the remaining parameters are the default parameters under Fine precision.

6. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 1, characterized in that, The microstructure and electronic properties of the modified carbon nanotubes include bond length, binding energy, electrostatic potential, dipole moment, energy level, and density of states.

7. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 1, characterized in that, The doping amount is the ratio of the number of carbon atoms in the functional group to the number of atoms in the carbon nanotube.

8. The method for evaluating the properties of surface-modified carbon nanotubes based on first-principles calculations according to claim 4, characterized in that, In step 4, the DMol3 module of MS software was used to perform geometric optimization on the modified carbon nanotube models with different doping gradients. During the calculation, GGA-PBE functionals were used for all-electronic structure calculations, and the DNP numerical basis set with polarization functions was selected. Dispersion correction was used to handle weak interactions between functional groups. The model was set to be unrestricted and symmetry was used for calculation, and temperature broadening was enabled. The convergence criterion for geometric optimization was: with fine precision, the system energy convergence criterion was 10e -5 Ha, force convergence tolerance is 0.002 Ha / Å, atomic displacement convergence standard is 0.005 Å, and the remaining parameters are the default parameters under Fine precision.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1 to 8.

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