X-RAY METHOD FOR STRUCTURE DETERMINATION OF EQUILIBRIUM SOLID-LIQUID SYSTEM. Yu.V. Agrafonov, F.E. Ushakov Department of Physics, Irkutsk State University, Irkutsk, Russia

A universal statistical approach for description of X-ray scattering by substance in any state of matter is suggested. X-ray scattering by solid and liquid phases is examined by different ways.

If solid is considered, dimensions of cell, location of lattice sites and electron distribution inside the cell are usually defined. The long-range order describes crystal state: unary distribution function defining location of atoms in lattice sites is a periodic one. X-rays are scattered on atomic planes.

For liquid the space distribution of moving particles is defined. The short-range order describing liquid structure is related to the density fluctuation that is completely predetermined by binary distribution function.

In our approach averaging over statistical ensemble leads to expression for scattered radiation intensity that include unary and binary distribution functions. This expression can be applied either for homogeneous or inhomogeneous systems.

When crystal is in equilibrium with its molten matter (liquid to solid transition), both long-range and short-range orders contribute to the scattering. The information about scattering (intensity of scattered radiation) being obtaining, the distribution functions of high-temperature crystal could be defined. Also the approach can be used for testing phase transition theories.