Theoretical Study for Crystal Structure Deformation in A^<i>N</i>B⁸^-^<i>N</i> Compounds

Abstract

The crystal-structure deformation depending on lattice parameters in A N B 8−N compounds is investigated on the basis of density-functional theory (DFT) calculations. Our DFT calculations for C, BN and BeO demonstrate that the energy difference in cohesive energy along crystal structure deformation path strongly depends on the ionicity fi of materials. In particular, the energy barriers for structural deformation from threefold coordinated (hexagonal graphite) to fourfold coordinated (wurtzite) structures in BN and C are marked, whereas that in BeO is negligible. The difference in the energy barrier originates from both repulsive interaction among bond charges and attractive interaction among ionic charges. The repulsive interaction among bond charges in C (fi = 0) results in the highest energy barrier of 0.39 eV, while the attractive interaction among ionic charges in BeO with large ionicity (fi = 0.602) does in quite small energy barrier. These results imply that the ionicity is crucial for determining the energy change along crystal deformation path as well as the structural stability.

Systematic approach to developing empirical interatomic potentials for III–N semiconductors

“…17) The valence electrons are expanded by the plane-wave basis set with a cutoff energy of 49 Ry that gives sufficient convergence of cohesive energies. Table I shows the cohesive energy (D e ) and equilibrium interatomic distance (r e ) values with experimental values of r e at Z = 4 for BN, [18][19][20] AlN, GaN, and InN 19,21,22) used in this study.…”

Systematic Theoretical Investigations for Crystal Structure Deformation in Group‐III Nitrides: A First‐Principles Study

“…Although the relative stability among various structures including Hex, WZ, zinc blende (ZB), and rocksalt (RS) structures in group‐III nitrides has been clarified, the crystal structure transformation among various structures still remains unclear. In our previous study, we have investigated the crystal structure deformation and its energy barrier in C, BN, and BeO . It has been found that the structural transformation originates from the ionicity of materials.…”

“…In our previous study, we have investigated the crystal structure deformation and its energy barrier in C, BN, and BeO. [10] It has been found that the structural transformation originates from the ionicity of materials. In this study, we extend our study to investigate the crystal structure deformation among Hex, WZ, and RS structures in group-III nitrides (BN, AlN, GaN, and InN) by using density functional theory (DFT) calculations.…”

Empirical interatomic potential approach to the stability of graphitic structure in ANB8−Ncompounds

“…1 where the cohesive energies from G to RS via WZ can be continuously obtained by varying axial ratios b/a and c/a with incorporating atomic volume change and atomic displacements in the unit cell. 16) We use the generalized gradient approximation (GGA) 17) and the normconserving pseudopotentials. 18) The valence electrons are expanded by the plane-wave basis set with a cutoff energy of 49 Ry that gives enough convergence of cohesive energies.…”