Stability and strength of covalent crystals under uniaxial and triaxial loading from first principles

Stability and strength of covalent crystals under uniaxial and triaxial loading from first principles

Článek WoS

Response of three covalent crystals with a diamond lattice (C, Si and Ge) to uniaxial and a special triaxial (generally nonhydrostatic) loading is calculated from first principles. The lattice deformations are described in terms of variations of bond lengths and angles. The triaxial stress state is simulated as a superposition of axial tension or compression and transverse (both tensile and compressive) biaxial stresses. The biaxial stresses are considered to be adjustable parameters and the theoretical strengths in tension and compression along <100>, <110>, <111> crystallographic directions are calculated as their functions. The obtained results revealed that the compressive strengths are, consistently to fcc metals, almost linear functions of the transverse stresses. Tensile transverse stresses lower the compressive strength and vice versa. The tensile strengths, however, are not monotonic functions of the transverse biaxial stresses since they mostly exhibit maxima for certain values of the transverse stresses (e.g., tensile for<100> and <110> loading of Si and Ge or compressive for <100> loading of C).

Response of three covalent crystals with a diamond lattice (C, Si and Ge) to uniaxial and a special triaxial (generally nonhydrostatic) loading is calculated from first principles. The lattice deformations are described in terms of variations of bond lengths and angles. The triaxial stress state is simulated as a superposition of axial tension or compression and transverse (both tensile and compressive) biaxial stresses. The biaxial stresses are considered to be adjustable parameters and the theoretical strengths in tension and compression along <100>, <110>, <111> crystallographic directions are calculated as their functions. The obtained results revealed that the compressive strengths are, consistently to fcc metals, almost linear functions of the transverse stresses. Tensile transverse stresses lower the compressive strength and vice versa. The tensile strengths, however, are not monotonic functions of the transverse biaxial stresses since they mostly exhibit maxima for certain values of the transverse stresses (e.g., tensile for<100> and <110> loading of Si and Ge or compressive for <100> loading of C).

theoretical strength, triaxial loading, diamond structure, ab initio calculations

theoretical strength, triaxial loading, diamond structure, ab initio calculations

ČERNÝ, M.; ŘEHÁK, P.; UMENO, Y.; POKLUDA, J.

2014

23.01.2013

0953-8984

JOURNAL OF PHYSICS-CONDENSED MATTER

25

3

Spojené království Velké Británie a Severního Irska

035401

035401

8