Compressibility and structural stability of ultra-incompressible bimetallic interstitial carbides and nitrides

High-pressure x-ray diffraction and ab initio study of Ni2Mo3N, Pd2Mo3N, Pt2Mo3N, Co3Mo3N, and Fe3Mo3N: Two families of ultra-incompressible bimetallic interstitial nitrides

We have studied by means of high-pressure x-ray diffraction the structural stability of Ni2Mo3N, Co3Mo3N, and Fe3Mo3N. We also report ab initio computing modeling of the high-pressure properties of these compounds, Pd2Mo3N, and Pt2Mo3N. We have found that the nitrides remain stable in the ambient-pressure cubic structure at least up to 50 GPa and determined their equation of state. All of them have a bulk modulus larger than 300 GPa. Single-crystal elastic constants have been calculated in order to quantify the stiffness of the investigated nitrides. We found that they should have a Vickers ha…

Control of spintronic and electronic properties of bimetallic and vacancy-ordered vanadium carbide MXenes via surface functionalization

MXenes are 2D transition metal carbides with high potential for overcoming limitations of conventional two-dimensional electronics. In this context, various MXenes have shown magnetic properties suitable for applications in spintronics, yet the number of MXenes reported so far is far smaller than their parental MAX phases. Therefore, we have studied the structural, electronic and magnetic properties of bimetallic and vacancy-ordered MXenes derived from a new $(V_{2/3}Zr_{1/3})_2AlC $ MAX phase to assess whether MXene exfoliation would return stable magnetic materials. In particular, we have in…

First principle study of intrinsic defects in hexagonal tungsten carbide

The characteristics of intrinsic defects are important for the understanding of self-diffusion processes, mechanical strength, brittleness, and plasticity of tungsten carbide, which present in the divertor of fusion reactors. Here, we use first-principles calculations to investigate the stability of point defects and their complexes in WC. Our calculation results confirm that the formation energies of carbon defects are much lower than that of tungsten defects. The outward relaxations around vacancy are found. Both interstitial carbon and interstitial tungsten atom prefer to occupy the carbon …

First principle study of hydrogen behavior in hexagonal tungsten carbide

Understanding the behavior of hydrogen in hexagonal tungsten carbide (WC) is of particular interest for fusion reactor design due to the presence of WC in the divertor of fusion reactors. Therefore, we use first-principles calculations to study the hydrogen behavior in WC. The most stable interstitial site for the hydrogen atom is the projection of the octahedral interstitial site on tungsten basal plane, followed by the site near the projection of the octahedral interstitial site on carbon basal plane. The binding energy between two interstitial hydrogen atoms is negative, suggesting that hyd…

有限温度下立方碳化硅中氢溶解度的密度泛函理论计算

Density-functional theory calculation of hydrogen solubility in cubic silicon carbide at finite temperatures

利用密度泛函理论从头算框架预测纯净和缺陷β-SiC中的氢溶解度，发现碳富集非化学计量非晶结构和硅空位显著增强氢溶解度。

Theoretical study of the recombination of Frenkel pairs in irradiated silicon carbide

The recombination of Frenkel pairs resulting from low energy recoils in 3C-SiC has been investigated using first principles and Nudged Elastic Band calculations. Several recombination mechanisms have been obtained, involving direct interstitial migration, atoms exchange, or concerted displacements, with activation energies ranging from 0.65 eV to 1.84 eV. These results are in agreement with experimental activation energies. We have determined the lifetime of the $V_{Si}+Si_{TC}$ Frenkel pair, by computing phonons and the Arrhenius prefactor. The vibrational contributions to the free energy bar…