Source code for pynao.m_fermi_dirac

from __future__ import print_function, division
from numpy import exp, copy, nditer

def fermi_dirac(telec, e, fermi_energy):
    """
    Fermi-Dirac distribution function
    """
    pw = (e-fermi_energy)/telec
    if pw > +100.0:
        return 0.0
    if pw < -100.0:
        return 1.0
    return 1.0/(1.0 + exp(pw))

def fermi_dirac_occupations(telec, ksn2e, fermi_energy):
    """
    Occupations according to the Fermi-Dirac distribution function.
    """
    assert telec>0.0
    ksn2f = copy(ksn2e)
    for e in nditer(ksn2f, op_flags=['readwrite']):
        e[...] = fermi_dirac(telec, e, fermi_energy)

    return ksn2f