facs -amplitude of the confinement operator

DESCRIPTION

The facs variable enters the expression of the confinement operator which is added to the Kohn-Sham hamiltonian when computing the stress tensor (when stress is set to ON). The confinement operator is diagonal in the plane wave basis 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 value of facs affects the value of the fictitious mass of the electronic degrees of freedom (emass) chosen automatically.

DEFAULT VALUE

2

ALLOWED VALUES

non-negative floating point

RELATED INFORMATION

stress, ecuts, sigmas, refcell, emass