def fCoreRepulsion(self):
    N = len(self.Elements)
    Charges = array([ElementNumbers[o] for o in self.Elements])
    fCoreEnergy = 0
    for i in range(N):
        for j in range(i):
            fCoreEnergy += self.fCoreRepulsion1(i, j)
    return fCoreEnergy
def fCoreRepulsion(self):
    N = len(self.Elements)
    Charges = array([ElementNumbers[o] for o in self.Elements])
    fCoreEnergy = 0
    for i in range(N):
        for j in range(i):
            fCoreEnergy += self.fCoreRepulsion1(i, j)
    return fCoreEnergy