A practical scheme for ab initio determination of a crystal structure based on the Dirac equation

An applicable formulation of ab initio crystal structure determination based on the Dirac equation is presented. For this purpose, Dirac equation without regard to electron correlation effects is reduced to its spin-free one-component form by means of regular approximations, and then, connected to crystallographic notions. Thus, a relativistically valid structural description of a crystal structure is made possible by using single crystal X-ray diffraction data. The relativistic scheme was tested with a previously reported crystal structure containing heavy elements, and the results show that accuracy of the phase assignment process increases as the order of regular approximation is raised.