def scale_kappa_DLPOLYtoSI(temp, volume, timestep):
    """
    Conversion factor for the thermal conductivity from DL_POLY units to SI units.
    INPUT:
    temp      =  temperature [ K ]
    volume    =  cell volume [ A^3 ]
    timestep  =  integration time step [ fs ]
    """
    kB = 1.3806504
    NA = 6.022140857
    return (1.0 / NA / temp) ** 2 / kB / volume * timestep * 10000000000.0
