stress variable

NAME

  stress -stress calculation control variable

DESCRIPTION

The stress variable controls the calculation of the stress tensor for optimization  of the cell parameters. If stress is set to ON, a confinement operator is added to the Kohn-Sham hamiltonian. The confinement operator is diagonal in the plane wave basis and and ensures that the resolution used for the description of the wavefunctions is independent of cell size.

H_conf(G) = facs * 0.5 * G2 * (1 - f((0.5*G2 - ecuts)/sigmas))

f(E) = 1 / ( 1 + exp(E) )
 

The effect of the confinement operator is to reduce the amplitude of the wavefunctions' Fourier coefficients for large wave vectors (G2 > ecuts).

DEFAULT VALUE

OFF

ALLOWED VALUES

ON, OFF

RELATED INFORMATION

ecuts, facs, sigmas, refcell,


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