properties_anis.py 文件源码

def compute_alpha(minT,ibrav):
    """
    This function calculates the thermal expansion alphaT at different temperatures
    from the input minT matrix by computing the numerical derivatives with numpy.
    The input matrix minT has shape nT*6, where the first index is the temperature 
    and the second the lattice parameter. For example, minT[i,0] and minT[i,2] are
    the lattice parameters a and c at the temperature i.

    More ibrav types must be implemented
    """

    grad=np.gradient(np.array(minT))  # numerical derivatives with numpy
    alphaT = np.array(grad[0])  # grad[0] contains the derivatives with respect to T, which is the first axis in minT
                                # also convert to np.array format

    # now normalize the alpha properly. It must be different for different ibrav
    # to avoid a divide by 0 error (minT is zero for lattice parameters not defined
    # in the system)
    if ibrav==4:
        alphaT[:,0] = alphaT[:,0]/minT[:,0]
        alphaT[:,2] = alphaT[:,2]/minT[:,2]

    return alphaT


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