Phonon stability of fcc crystals under hydrostatic loading

Phonon stability of fcc crystals under hydrostatic loading

abstract

en

Lattice dynamics and stability of four fcc crystals (Al, Ir, Pt, and Au) under isotropic (hydrostatic) tensile loading is studied from first principles using the linear response method and the harmonic approximation. A relevant analysis of elastic stability conditions is also performed and the results obtained by means of both approaches are compared. The results reveal that, contrary to former expectations, strengths of all the studied crystals are limited by instabilities related to soft phonons with finite or vanishing wave vectors. The critical strains associated with such instabilities are remarkably lower than those related to the volumetric instability. On the other hand, the corresponding reduction of the tensile strength is by 20 % at the most.

Lattice dynamics and stability of four fcc crystals (Al, Ir, Pt, and Au) under isotropic (hydrostatic) tensile loading is studied from first principles using the linear response method and the harmonic approximation. A relevant analysis of elastic stability conditions is also performed and the results obtained by means of both approaches are compared. The results reveal that, contrary to former expectations, strengths of all the studied crystals are limited by instabilities related to soft phonons with finite or vanishing wave vectors. The critical strains associated with such instabilities are remarkably lower than those related to the volumetric instability. On the other hand, the corresponding reduction of the tensile strength is by 20 % at the most.

Lattice dynamics and stability of four fcc crystals (Al, Ir, Pt, and Au) under isotropic (hydrostatic) tensile loading is studied from first principles using the linear response method and the harmonic approximation. A relevant analysis of elastic stability conditions is also performed and the results obtained by means of both approaches are compared. The results reveal that, contrary to former expectations, strengths of all the studied crystals are limited by instabilities related to soft phonons with finite or vanishing wave vectors. The critical strains associated with such instabilities are remarkably lower than those related to the volumetric instability. On the other hand, the corresponding reduction of the tensile strength is by 20 % at the most.

phonon instability, theoretical strength, isotropic loading

phonon instability, theoretical strength, isotropic loading

11.07.2012

Nantes (FR)

ICAMM 2012 and VASP workshop

106–108

3