An analysis method for diffusion of hydrogen atoms in rare earth element-doped iron

Abstract

The application discloses an analysis method for diffusion of hydrogen atoms in rare earth element doped iron, which comprises the following steps: establishing a unit cell model of metal iron; analyzing a pseudo-potential file to obtain plane wave cutoff energy information; using a first principle calculation method, optimizing the structure of the unit cell model to obtain a stable unit cell structure and lattice parameters; doping rare earth elements in the stable unit cell structure and optimizing the structure to obtain a stable doped structure; adding hydrogen atoms in the stable doped structure, calculating the binding energy of the hydrogen atoms in different doped positions, and finding the most stable existing position of the hydrogen atoms; according to the possible existing positions of the hydrogen atoms, calculating the transition state in the diffusion process of the hydrogen atoms, and calculating the diffusion path and diffusion barrier; and performing electronic performance calculation to analyze the changes of electron transfer and atomic bonding before and after the hydrogen atoms are doped. The application analyzes the diffusion of hydrogen atoms in the rare earth element doped iron from the perspective of calculation, and lays a foundation for solving the hydrogen embrittlement problem.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen atom diffusion analysis in iron, and particularly relates to a method for analyzing hydrogen atom diffusion in iron doped with rare earth elements. BACKGROUND

[0002] Hydrogen is easy to enter metal materials, which reduces the mechanical properties of the materials and causes brittle failure, which is referred to as hydrogen embrittlement. With the increasingly harsh environment of materials, in some high-pressure hydrogen storage and oil refining equipment, how to prevent hydrogen embrittlement has become an important topic.

[0003] At present, people have proposed various mechanisms to try to explain this phenomenon, such as hydrogen-induced weak bond theory, hydrogen pressure theory, hydrogen-induced surface energy reduction theory, hydrogen-induced phase transition theory, and hydrogen-induced local plastic deformation theory, but the above theories for describing hydrogen embrittlement all have their applicable scope and object, and have great limitations. SUMMARY

[0004] Therefore, the present application provides a method for analyzing hydrogen atom diffusion in iron doped with rare earth elements, which calculates the diffusion performance of hydrogen atoms in iron doped with rare earth elements, studies the diffusion of hydrogen atoms in iron doped with rare earth elements, and essentially analyzes the hydrogen embrittlement phenomenon to solve the problem of hydrogen embrittlement.

[0005] The present application adopts the following scheme to achieve the above-mentioned technical problems:

[0006] The present application provides a method for analyzing hydrogen atom diffusion in iron doped with rare earth elements, which includes:

[0007] Establishing a crystal unit cell structure of metal iron, optimizing the lattice parameters of the unit cell, and obtaining the lattice parameters of the stable unit cell;

[0008] Based on the stable unit cell, a unit cell model is established;

[0009] Analyzing the pseudo-potential file to obtain the plane wave cutoff energy information, using the first-principles calculation method, optimizing the structure of the unit cell model, and obtaining the stable unit cell structure and lattice parameters;

[0010] Doping rare earth elements in the stable unit cell structure and optimizing the structure to obtain a stable doped structure;

[0011] Adding hydrogen atoms to the stable doped structure, calculating the binding energy of hydrogen atoms at different doped positions by the NEB method, and finding the most stable position of hydrogen atoms;

[0012] According to the possible positions of hydrogen atoms, the transition state in the diffusion process of hydrogen atoms is calculated, and the diffusion path and diffusion barrier are calculated;

[0013] Perform electronic performance calculation, analyze the change of electron transfer and atomic bonding before and after hydrogen atom incorporation.

[0014] Further, the binding energy calculation formula is:

[0015] E coh = E total – E s – E H ;

[0016] Wherein E coh is the binding energy, E s is the total energy of the stable doped system before hydrogen atom incorporation, E H is the energy of a single hydrogen atom, E total is the total energy of the stable doped system after hydrogen atom incorporation.

[0017] Further, the electronic performance calculation includes: bader charge, differential charge and state density calculation.

[0018] Further, in the electronic performance calculation, the differential charge density calculation formula is:

[0019] Δρ=ρ AB –ρ A –ρ B ;

[0020] Wherein, Δρ is the differential charge density, ρ AB is the charge density of the stable doped system after hydrogen atom incorporation, ρ A is the charge density of the stable doped system before hydrogen atom incorporation, and ρ B is the charge density of the water molecule.

[0021] Further, the lattice parameters of the unit cell are optimized, including: full relaxation optimization of the iron crystal unit cell.

[0022] Further, the crystal cell model is optimized by using Materials Studio software.

[0023] Further, the rare earth element is incorporated in the stable crystal cell structure, including:

[0024] The rare earth element is incorporated in the stable crystal cell structure in a substitutional doping manner.

[0025] Further, hydrogen atoms are added to the stable doped structure, including:

[0026] Hydrogen atoms are added to the stable doped structure in an interstitial doping manner.

[0027] The hydrogen atom in the rare earth element doped iron diffusion analysis method provided by the present application has the advantages and positive effects that: in the present application, firstly, a reasonable unit cell model is constructed by software modeling, rare earth elements are doped in the unit cell model, then hydrogen atoms are doped in the unit cell model after doping, the binding energy is calculated by the first principle calculation method, so as to determine the most stable position of the hydrogen atom in the unit cell, and then the transition state calculation is carried out to determine the diffusion path and diffusion barrier of the hydrogen atom in the rare earth element doped iron. Finally, the change of the bonding between the hydrogen atom and the surrounding atoms after the hydrogen atom is doped is analyzed by electronic performance calculation. The present application analyzes the diffusion of the hydrogen atom in the rare earth element doped iron from the calculation point of view, which lays a foundation for solving the hydrogen embrittlement problem. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] Figure 1 The flow chart of the hydrogen atom in the rare earth element doped iron diffusion analysis method in the embodiment of the present application;

[0030] Figure 2 The model diagram of the hydrogen atom in the iron unit cell after the rare earth Y element is doped in a typical example in the embodiment of the present application when the hydrogen atom is stably present;

[0031] Figure 3 The differential charge density diagram of the hydrogen atom in the iron unit cell after the rare earth Y element is doped in a typical example in the embodiment of the present application when the hydrogen atom is stably present. DETAILED DESCRIPTION

[0032] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0033] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application and the above-described drawings are used to distinguish similar objects and are not necessarily used to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged, where appropriate, so that the embodiments of the application described herein can be carried out in other than the order shown or described herein. Moreover, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, processes, methods, systems, products, or devices that include a series of steps or units without necessarily being limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0034] Essentially, hydrogen embrittlement is caused by the interaction of hydrogen and metal, including the adsorption and dissociation behavior of the environmental medium on the metal surface, the diffusion behavior of hydrogen atoms in the matrix after entering the metal material, and the influence of hydrogen atoms on the metal deformation behavior. The first principle calculation method provides an effective and feasible means for studying the micro mechanism of the interaction between hydrogen and metal matrix.

[0035] As shown in Figure 1 The present application provides a method for analyzing the diffusion of hydrogen atoms in rare earth element-doped iron, based on the first principle calculation method to study the diffusion of hydrogen atoms in rare earth element-doped iron, including the following steps:

[0036] Step one: establish the crystal cell structure of metal iron, optimize the lattice parameters of the cell, and obtain the lattice parameters of the stable cell. Based on the stable cell, establish the required cell model.

[0037] In some embodiments, to obtain accurate metal cell lattice constants, the iron crystal cell in step one needs to be fully relaxed and optimized.

[0038] Step two: analyze the pseudo-potential file to obtain the plane wave cutoff energy information, use the first principle calculation method to optimize the structure of the cell model constructed in step one, and obtain the stable cell structure and lattice parameters.

[0039] In some embodiments, step two includes: analyzing the pseudo-potential file to obtain the plane wave cutoff energy information, using the Materials Studio software to optimize the structure of the cell model in step two, obtaining the stable cell structure and cell parameters, and only optimizing the atomic positions when optimizing the cell model, not optimizing the cell structure.

[0040] Step three: incorporate rare earth elements into the stable cell structure obtained in step two and optimize the structure to obtain the stable cell structure of the doped system.

[0041] In some embodiments, step three comprises: incorporating rare earth elements into the stable unit cell structure obtained in step two, taking substitutional doping as an example, optimizing the doped unit cell structure to obtain a stable doped unit cell structure. The parameter settings during optimization are consistent with those in step two.

[0042] Step four: adding hydrogen atoms to the stable doped unit cell obtained in step three, finding the positions where hydrogen atoms can stably exist, and calculating the binding energy of hydrogen atoms.

[0043] In some embodiments, step four comprises: adding hydrogen atoms to the stable doped unit cell obtained in step three, wherein, in the present example, hydrogen atoms are taken as an example of interstitial doping, and the interstitial types in the iron unit cell include tetrahedral interstitials and octahedral interstitials. In order to obtain the optimal binding position of hydrogen atoms, the binding energy of hydrogen atoms in octahedral interstitials and tetrahedral interstitials is calculated respectively, and whether hydrogen atoms can stably exist in each interstitial is determined according to the structure optimization results. Figure 2 The model diagram of hydrogen atoms stably existing in the iron unit cell after doping with rare earth Y elements is shown as a typical example, Figure 2 (a) is a top view, Figure 2 (b) is a front view.

[0044] The binding energy calculation formula is:

[0045] E coh = E total – E s – E H (1)

[0046] Where E coh is the binding energy, E s is the total energy of the stable doped system before the hydrogen atom is incorporated, E H is the energy of a single hydrogen atom, and E total is the total energy of the stable doped system after the hydrogen atom is incorporated. The binding energy of possible sites of hydrogen atoms in pure iron and iron unit cells after doping with Y and La elements is shown in Table 1.

[0047] Step five: based on the positions where hydrogen atoms can exist in step four, find the transition state of hydrogen atoms during diffusion by NEB calculation, and calculate the diffusion path and diffusion barrier.

[0048] In some embodiments, step five comprises: based on the stable model of hydrogen atoms doped in different interstitial positions in step five, using Materials Studio software to calculate the transition state of hydrogen atoms, and calculating the diffusion path and diffusion barrier. NEB (nudged elastic band) is a method for finding saddle points and minimum energy paths with known reactants and products. With NEB, the diffusion path or diffusion barrier, transition state can be calculated.

[0049] Step six: perform electronic performance calculation, analyze the change of bonding performance of the surrounding atoms after the hydrogen atom enters.

[0050] In some schemes, step six includes: according to the most stable structure obtained in step five, performing bader charge, differential charge and state density calculation, observing the electronic transfer of the system after the hydrogen atom is incorporated by the bader charge and differential charge results, and analyzing the change of the bonding properties of the system before and after the hydrogen incorporation according to the state density results. Figure 3 Fig. 1 is a differential charge density diagram of a typical example of the hydrogen atom stably existing in the iron unit cell after being doped with a rare earth Y element, wherein the blue part represents charge dissipation, and the yellow part represents charge aggregation, and it can be seen that the hydrogen atom obtains electrons, and the iron atoms and Y atoms near the hydrogen atom lose electrons.

[0051] Differential charge density calculation formula:

[0052] Δρ = ρ AB - ρ A - ρ B (2)

[0053] Wherein, Δρ is the differential charge density, ρ AB is the charge density of the stable doped system after the hydrogen atom is incorporated, ρ A is the charge density of the stable doped system before the hydrogen atom is incorporated, and ρ B is the charge density of the water molecule.

[0054] Table 1

[0055]

[0056] The software used in the examples includes Materials Studio and VESTA.

[0057] In the above examples, first, a reasonable unit cell model is constructed by software modeling, a rare earth element is incorporated in the unit cell model, then a hydrogen atom is incorporated in the doped unit cell model, the binding energy is calculated by the first principle calculation method, so as to determine the most stable position of the hydrogen atom in the unit cell, and then the transition state calculation is performed to determine the diffusion path and diffusion barrier of the hydrogen atom in the rare earth element doped iron. Finally, the change of the bonding between the hydrogen atom and the surrounding atoms after the hydrogen atom is incorporated is analyzed by electronic performance calculation. The present application analyzes the diffusion of the hydrogen atom in the rare earth element doped iron from the perspective of calculation, and lays a foundation for solving the hydrogen embrittlement problem.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An analytical method for the diffusion of hydrogen atoms in rare earth element-doped iron, characterized in that, The analytical method includes: Establish the crystal unit cell structure of metallic iron, optimize the lattice parameters of the unit cell, and obtain the lattice parameters of a stable unit cell; Based on the stable unit cell, a unit cell model is established; The plane wave cutoff energy information is obtained by analyzing the pseudopotential file. The cell model is then optimized using first-principles calculations to obtain a stable cell structure and lattice parameters. Rare earth elements are incorporated into the stable cell structure, and the structure is optimized to obtain a stable doped structure. Hydrogen atoms are added to the stable doped structure, and the binding energy of hydrogen atoms at different doping sites is calculated using the NEB method to find the site where hydrogen atoms are most stable. Based on the possible locations of hydrogen atoms, calculate and find the transition states in the hydrogen atom diffusion process, and calculate the diffusion path and diffusion barrier; Perform electronic property calculations to analyze changes in electron transfer and atomic bonding before and after hydrogen atom incorporation; The formula for calculating the binding energy is: E coh = E total – E s – E H ； in E coh It is the binding energy. E s E is the total energy of the stable doped system before the introduction of hydrogen atoms. H It is the energy of a single hydrogen atom. E total It is the total energy of the stable doped system after hydrogen atoms are incorporated; The electronic performance calculations include: Bader charge, differential charge, and density of states calculations; the differential charge density calculation formula is as follows: Dr = p AB – r A – r B ; Where Δρ is the differential charge density, ρ AB It is the charge density of the stable doped system after hydrogen atom doping, ρ A It is the charge density of the stable doped system before hydrogen atom incorporation, ρ B It is the charge density of water molecules.

2. The analytical method for the diffusion of hydrogen atoms in rare earth element-doped iron according to claim 1, characterized in that, The lattice parameters of the unit cell are optimized, including full relaxation optimization of the iron crystal unit cell.

3. The analytical method for the diffusion of hydrogen atoms in rare earth element-doped iron according to claim 1, characterized in that, The cell model was structurally optimized using Materials Studio software.

4. The analytical method for the diffusion of hydrogen atoms in rare earth element-doped iron according to claim 1, characterized in that, The doping of rare earth elements into the stable unit cell structure includes: Rare earth elements are incorporated into the stable cell structure in a manner that replaces doping.

5. The analytical method for the diffusion of hydrogen atoms in rare earth element-doped iron according to claim 1, characterized in that, Adding hydrogen atoms to the stable doped structure includes: Hydrogen atoms are added to the stable doped structure via interstitial doping.

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