Collective Dynamics Of Liquid Mg And Ca

The collective dynamic properties of liquid Mg i Ca near their melting points are studied. For the description of interionic interaction the pair potential based on the Fiolhais pseudopotential [C. Fiolhais, J.P. Perdew, S.Q. Armster, J.M. MacLaren M. Brajczewska, Phys. Rev. B 5 1, 14001 (1995)] is applied. Using the method of molecular dynamics such characteristics as dynamic structural factors and longitudinal time- dependent current correlation functions are calculated. From the Fourier transforms of the corresponding correlation functions the phonon dispersion relations are obtained and the values of sound velocity of considered metals are estimated. Simultaneously, the dispersion relations are calculated theoretically using the expressions of Takeno and Goda [S. Takeno, M. Goda, Prog. Theor. Phys. 4 5, 331 (1971)] from which the sound velocities are obtained as well. It is observed that the values of sound velocity calculated in this study are somewhat overestimated in comparison with experimental data, and it can be explained by the shortcoming of the potentials which were applied.