一、引言晶体内部的电子密度函数ρ(r)决定了它的衍射图象,即晶体的 X-射线各衍射方向振幅和相位,反过来,衍射图象同样也决定晶体的电子密度函数 p(r)。然而因为从衍射实验中只能得到一组强度值(振幅),所以电子密度函数ρ(r)就不能够求得。假如引用以前已知的结构知识,即晶体是由分立的已知原子序数的 I. INTRODUCTION The electron density function ρ (r) inside a crystal determines its diffraction pattern, the amplitude and phase of each X-ray diffraction direction of the crystal. In turn, the diffraction pattern also determines the electron density function p r). However, since only one set of intensity values ​​(amplitudes) can be obtained from the diffraction experiment, the electron density function ρ (r) can not be obtained. If we refer to the previously known structural knowledge, that is, the crystal is composed of discrete known atomic numbers