Structural, electronic, and elastic properties of K-As compounds: a first principles study

Abstract

First-principle calculations are performed to investigate the structural, elastic and electronic properties of K-As compounds (KAs in NaP, LiAs and AuCu-type structures, KAs(2) in MgCu(2)-type structure, K(3)As in Na(3)As, Cu(3)P and Li(3)Bi-type structures, and K(5)As(4) in A(5)B(4)-type structure). The lattice parameters, cohesive energy, formation energy, bulk modulus, and the first derivative of bulk modulus (to fit to the Murnaghan's equation of state) of the considered structures are calculated and reasonable agreement is obtained, and the phase transition pressure is also predicted. The repeated calculations on the electronic band structures and the related partial density of states are also given. The calculated second-order elastic constants based on the stress-strain method and the other related quantities such as Young's modulus, shear modulus, Poisson's ratio, sound velocities, Debye temperature, and shear anisotropy factors for considered structures are presented, and trends are discussed.

Metastable phases, phase transformation and properties of AlAs based on first-principle study

“…The value of B agrees well with 24 the fitted value of derived from the BM-EOS, suggesting the calculation is correct. B and G 25 represents the capacity to resist volume change under load and reversible deformations upon shear 26 stress [46]. Among three newly discovered AlAs polymorphs, oC12-AlAs exhibits the similar B, G 27 and E with hP6-AlAs, whereas cI24-AlAs has the smallest B, G and E. Generally speaking, a higher 11 E denotes a stiffer material, which indicating that hP6-AlAs and oC12-AlAs are both stiffer than 1 cI24-AlAs.…”

Superhard B2CO phases derived from carbon allotropes

“…B and G can be acquired by independent elastic parameter, then E and m can be obtained by B and G. 37 Generally speaking, B represents the ability to resist volume deformation by loading pressure, G characterizes the ability to resist deformation upon shear stress. 38 Both oP16-, and oC16-B 2 CO have very large B ($300 GPa) and G (above 240 GPa), indicating the excellent resistance to volume deformation by pressure stress and shear stress. Elastic anisotropy can give a prediction of the arrangement of the atoms in each direction, the bonding properties, and some chemical characteristics in different directions of materials.…”

Theoretical Study of Novel B2CO Compounds with High Hardness

“…Generally, shear modulus G can be acquired by independent elastic parameter, [36] represents the ability to resist deformation upon shear stress. [35] Due to the structural differences, the shear modulus G of oP8' is smaller than that of mP16 at AP. As exhibited in Fig.…”

“…Because mP16 is composed of pure sp 3 hybridization, which is denser than oP8' formed by the coexistence of sp 2 and sp 3 hybridization. Generally, B indicates the ability to resist volume deformation by loading pressure, [35] and can be calculated by independent elastic parameter.…”