independent_sphere.py 文件源码

def ft_autocorrelation_function(self, k):
        """Compute the 3D Fourier transform of the isotropic correlation
        function for an independent sphere for given magnitude k of the 3D wave vector
        (float).

        """

        X = self.radius * np.asarray(k)
        volume_sphere = 4.0 / 3 * np.pi * self.radius**3

        bessel_term = np.empty_like(X)
        zero_X = np.isclose(X, 0)
        non_zero_X = np.logical_not(zero_X)
        X_non_zero = X[non_zero_X]

        bessel_term[non_zero_X] = (9 * ((np.sin(X_non_zero) - X_non_zero * np.cos(X_non_zero))
                                        / X_non_zero**3)**2)
        bessel_term[zero_X] = 1.0
        return self.corr_func_at_origin * volume_sphere * bessel_term