Characterization method based on neptunium-containing compound

Abstract

The invention relates to the technical field of physics, chemistry and materials, in particular to a characterization method based on a neptunium-containing compound. The characterization method comprises the following steps: carrying out total potential energy first principle calculation on the neptunium-containing compound by adopting a total potential linearization enhanced plane wave and local orbit method; under the framework of a density functional theory, an exchange association functional and / or a hybrid functional are / is adopted, and meanwhile, a relativistic effect is introduced through spin-orbit coupling; the electronic characteristics and the magnetic field characteristics of the neptunium-containing compound are obtained; wherein the neptunium-containing compound is a neptunium monometal compound.

Description

Technical Field

[0001] This disclosure relates to the fields of physics, chemistry and materials science, and in particular to a characterization method based on neptunium-containing compounds. Background Technology

[0002] For neptunium monometallic compounds, especially for neptunium monophosphorides (NpX, where X is selected from N, P, As, Sb), they belong to the NaCl type simple cubic structure, but due to the presence of 5f electrons in their structure, they exhibit complex magnetic order (ferromagnetic, antiferromagnetic, etc.) and heavy fermion behavior. Experiments have been conducted to determine the Curie / Nier temperature, magnetic moment and hyperfine field of these materials using neutron diffraction, Mössbauer spectroscopy and nuclear magnetic resonance, but the data given by different techniques are inconsistent or have gaps.

[0003] Currently, there is no systematic first-principles calculation framework that simultaneously encompasses structure, electronics, magnetism, electric field gradient (EFG), and hyperfine field (HFF). Traditional local density approximation (LDA) and generalized gradient approximation (GGA) suffer from significant discrepancies between experimental results and those of magnetic moments, EFG, and HFF due to self-interaction errors and the failure to consider relativistic effects (SOC). Furthermore, the lack of theoretical prediction models for the EFG and HFF of neptunium monophosphide series makes it impossible to explain these experimental differences. Moreover, the presence of 5f electrons leads to strong spatial expansion of the 5f electron wavefunction, resulting in complex coupling with conduction electrons and the lattice environment, which poses challenges for theoretical modeling.

[0004] Therefore, existing studies are scattered and lack precision. There is an urgent need for a unified computational characterization method with high precision, full potential energy, and including relativistic and strongly correlated corrections, to comprehensively characterize, explain, and predict the relationship between the structure and properties of neptunium monophosphoric compounds. Summary of the Invention

[0005] This disclosure provides a characterization method based on neptunium-containing compounds to address the shortcomings of related technologies.

[0006] According to a first aspect of the present disclosure, a characterization method based on neptunium-containing compounds is provided, the characterization method comprising the following: The neptunium-containing compound was subjected to first-principles calculations of its full potential energy using the full-potential linearization enhanced plane wave plus local orbit method. Furthermore, within the framework of density functional theory, exchange-correlated functionals and / or mixed functionals were employed, while relativistic effects were introduced through spin-orbit coupling. The electronic and magnetic properties of the neptunium-containing compound were obtained. The neptunium-containing compound was selected from neptunium monometallic compounds.

[0007] In one aspect of this disclosure, the neptunium monometallic compound has the chemical formula NpX, wherein X is selected from nitrogen, phosphorus, arsenic, or antimony.

[0008] In one aspect of this disclosure, the neptunium monometallic compound is selected from neptunium arsenide.

[0009] In one aspect of this disclosure, the exchange-correlation functional includes at least one of the local density approximation method, the generalized gradient approximation method, and the generalized gradient approximation + Hubbard U correction method.

[0010] In one aspect of this disclosure, the hybrid functional includes the Haydock-Cohen hybrid functional method and / or the Heyd-Scuseria-Ernzerhof 06 hybrid functional method.

[0011] In one aspect of this disclosure, the characterization method includes the following: The neptunium monometallic compound was subjected to first-principles calculations of its full potential energy using the full-potential linearization enhanced plane wave plus local orbit method. Furthermore, within the framework of density functional theory, exchange-correlated functionals and / or hybrid functionals were employed, while relativistic effects were introduced through spin-orbit coupling. The electronic and magnetic properties of the neptunium monometallic compound were obtained. The neptunium monometallic compound has the chemical formula NpX, wherein X is selected from nitrogen, phosphorus, arsenic or antimony; The exchange-correlation functional includes at least the generalized gradient approximation + Hubbard U correction method; The hybrid functionals include the Haydock-Cohen hybrid functional method.

[0012] In one aspect of this disclosure, the full potential linearization enhanced plane wave plus local orbit method includes: performing high-precision modeling of the neptunium-containing compound material, dividing the material's unit cell into muffin spheres and interstitial regions, and designing parameter optimization for the atoms of each element contained in the material.

[0013] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects: In the prior art, there is no existing technology that can simultaneously and systematically analyze the structure, electronic properties, magnetic properties, electric field gradient (EFG), and hyperfine field (HFF) of neptunium monophosphides. As can be seen from the above embodiments, this disclosure provides a unified computational characterization method that covers high precision, full potential energy, and includes relativistic and strongly correlated corrections. This method can well and comprehensively characterize, explain, and predict the relationship between the structure and properties of the neptunium monophosphide series. This disclosure can obtain a more accurate total magnetic moment of neptunium atoms compared to the prior art, and can better predict the electronic properties and magnetic properties of neptunium monophosphides.

[0014] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0016] Figure 1 This is a schematic diagram of a single cell as shown in Examples 1 to 4.

[0017] Figure 2 The curves showing the change in energy with volume are based on Examples 1 to 4.

[0018] Figure 3 It is a spin-resolved band structure calculated at the level of HF-WC hybrid functional + SOC (spin-orbit coupling) shown in Examples 1 to 4.

[0019] Figure 4 The magnetic moment values ​​are based on those shown in Examples 1 to 4.

[0020] Figure 5 This is a comparison of experimental values ​​of the hyperfine field (HFF) at the Np site with different calculation methods, as shown in Examples 1 to 4. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0024] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0025] In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0026] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0027] Unless otherwise stated, the terms used in this disclosure have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this disclosure can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this disclosure).

[0028] The term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0029] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0030] The present disclosure is further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure.

[0031] Example: Example 1: We provide neptunite NpAs; using the FP-LAPW (Full Potential Linearized Added Plane Wave) method integrated in the WIEN2k package, we calculate the structure, electronic, magnetic, and EFG properties of NpAs; we perform calculations of structures with and without spin-orbit coupling (SOC) under two exchange-correlation functionals, LDA and GGA (PBEsol); and we calculate the magnetic properties of NpAs using GGA+U and HF-WC hybrid functionals with added SOC.

[0032] Example 2: The steps of Example 2 are basically the same as those of Example 1, except that Example 2 uses NpN instead of NpAs.

[0033] Example 3: The steps of Example 3 are basically the same as those of Example 1, except that NpP is used instead of NpAs in Example 3.

[0034] Example 4: The steps of Example 4 are basically the same as those of Example 1, except that NpSb is used instead of NpAs in Example 4.

[0035] The structural properties of Examples 1 to 4 are as follows Figure 1As shown in the diagrams, in the single-cell schematics of Examples 1 to 4, Np is located at (0, 0, 0), and X(N, P, As, Sb) is located at (0.5, 0.5, 0.5); both are NaCl-type face-centered cubic (fcc) structures with space group Fm-3m (No. 225). In Example 2, all corner and face-centered sites are Np, and all body-centered and edge-centered sites are N. Due to the smallest atomic size of N, its symbol density is high and its arrangement is compact, making the contrast between N and Np in the diagram appear particularly dense. Each Np is coordinated by 6 N octahedra, and vice versa, forming a typical 6:6 coordinated NaCl structure. In Example 3, the covalent radius of P is greater than that of N, and its lattice constant is larger than that of NpN, which is reflected in the diagram as a slight increase in interatomic spacing. In Example 1, the As atomic symbol is larger than that of P, and the spacing is further increased, but the overall structure still maintains a cubic close-packed structure. In Example 4, Sb has the largest atomic radius and the largest lattice constant among the four elements. All compounds in Examples 1 to 4 maintained the NaCl-type 6:6 coordination, but the increased size of the X atom led to an increase in the Np–X bond length, affecting the magnetic exchange interaction and the degree of overlap with the 5f- orbital.

[0036] The energy versus volume curves of Examples 1 to 4 are shown below. Figure 2 As shown; and calculated using two exchange-correlation functionals: GGA (without spin-orbit coupling) and GGA+SOC (with spin-orbit coupling); the horizontal axis corresponds to the cell volume under different compression / expansion states; the vertical axis corresponds to the total energy of the system, with a larger negative value indicating greater stability; the lowest point of the obtained curve corresponds to the energy minimum; the minimum point of GGA in Example 1 is approximately 190 a.u.³, and the curve of GGA+SOC basically coincides with the curve of GGA, indicating that SOC has little effect on the equilibrium volume, which is also because NpN has the smallest volume, consistent with the fact that N atoms have the smallest radius. Figure 2 This demonstrates that the SOC effect provides additional stabilization for all compounds, primarily affecting energy.

[0037] Figure 3 The spin-resolved band structures for Examples 1 to 4 are calculated at the HF-WC hybrid functional + SOC (spin-orbit coupling) level; for Example 2, both the 5f↑ and 5f↓ bands cross E FThis results in the formation of semi-metallic or quasi-metallic characteristics; an exchange split of approximately 0.5 eV is visible above the Γ point, reflecting the local magnetic moment of Np-5f; Rashba-like splitting occurs in the WK segment, confirming the significant influence of SOC on the band shape. For Example 3, an indirect narrow bandgap of approximately 0.2 eV appears in the Γ-L direction (↓ channel), while the ↑ channel remains metallic, exhibiting a semi-metallic-narrow-gap semiconductor transition, with its 5f bandwidth slightly narrower than NpN, consistent with the weakening of 5f overlap due to lattice expansion. For Example 1, the ↑ channel remains metallic; the ↓ channel exhibits an indirect bandgap of 0.4 eV in the Γ-L direction, further increasing the bandgap. For Example 4, the Γ-L indirect bandgap of the ↓ channel is approximately 0.6 eV; the ↑ channel remains metallic, exhibiting a complete semi-metallic-semiconductor transition, with its 5f bandwidth being the narrowest, corresponding to the maximum lattice constant; the Sb-p and Np-5f hybridization is weaker, resulting in the valence band top being further away from E. F At point H, the spin-orbit splitting can reach 0.4 eV, which makes a significant contribution to the magnetic anisotropy (MAE). Figure 3 The study clearly demonstrated that the increase in lattice constant leads to enhanced 5f localization and band gap opening, and proved that the HF-WC+SOC method can accurately capture the complex 5f electronic behavior of neptunium monometallic compounds.

[0038] Figure 4 The magnetic moments of Examples 1 through 4 are shown in comparison. Figure 4 This demonstrates that the HF-WC+SOC method can quantitatively calculate the experimental magnetic moment of NpX, proving the prediction accuracy of this invention in strongly correlated 5f systems; GGA+U still retains significant self-interaction errors and does not fully account for the redistribution of orbital magnetic moments caused by SOC; the HF-WC hybrid functional reduces self-interactions; SOC correctly decomposes 5f orbital degeneracy and accurately gives the contribution of orbital magnetic moments.

[0039] Figure 5 The experimental values ​​of the hyperfine field (HFF) at the Np site of neptunium monometallic compounds are compared with those calculated using different methods. It can be seen that the deviation of GGA (without SOC) is about 15-20%; the deviation of GGA+SOC is reduced to 5-7%, but it still deviates significantly from the experiment; HF-WC+SOC almost coincides with the experimental value, proving that HF-WC+SOC is the key to accurately describing the 5f electron hyperfine interaction.

[0040] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A characterization method based on neptunium-containing compounds, characterized in that, The characterization method includes the following: The neptunium-containing compound was subjected to first-principles calculations of its full potential energy using the full-potential linearization enhanced plane wave plus local orbit method; and within the framework of density functional theory, exchange-correlated functionals and / or mixed functionals were employed, while relativistic effects were introduced through spin-orbit coupling. The electronic and magnetic field properties of the neptunium-containing compound were obtained; The neptunium-containing compound is selected from neptunium monometallic compounds.

2. The characterization method based on neptunium-containing compounds according to claim 1, characterized in that, The neptunium monometallic compound has the chemical formula NpX, wherein X is selected from nitrogen, phosphorus, arsenic or antimony.

3. The characterization method based on neptunium-containing compounds according to claim 1, characterized in that, The neptunium monometallic compound is selected from neptunium arsenide.

4. The characterization method based on neptunium-containing compounds according to claim 1, characterized in that, The exchange-correlation functional includes at least one of the local density approximation method, the generalized gradient approximation method, and the generalized gradient approximation + Hubbard U correction method.

5. The characterization method based on neptunium-containing compounds according to claim 1, characterized in that, The hybrid functionals include the Haydock-Cohen hybrid functional method and / or the Heyd-Scuseria-Ernzerhof 06 hybrid functional method.

6. The characterization method based on neptunium-containing compounds according to any one of claims 1-5, characterized in that, The characterization method includes the following: The full potential energy of the neptunium monometallic compound was calculated using the full potential linearization enhanced plane wave plus local orbit method; and within the framework of density functional theory, exchange-correlated functionals and / or hybrid functionals were used, while relativistic effects were introduced through spin-orbit coupling. The electronic and magnetic field properties of the neptunium monometallic compound were obtained; The neptunium monometallic compound has the chemical formula NpX, wherein X is selected from nitrogen, phosphorus, arsenic or antimony; The exchange-correlation functional includes at least the generalized gradient approximation + Hubbard U correction method; The hybrid functionals include the Haydock-Cohen hybrid functional method.

7. The characterization method based on neptunium-containing compounds according to claim 1, characterized in that, The full potential linearization enhanced plane wave plus local orbit method includes: performing high-precision modeling of the neptunium-containing compound material, dividing the material's unit cell into muffin spheres and interstitial regions, and designing parameter optimization for the atoms of each element contained in the material.

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