Calculation of thermodynamic properties of liquid alkali metals by the first-principle-pseudopotential and Weeks-Chandler-Andersen methods

Abstract

339 The methods of thermodynamic perturbation the� ory (TPT) combined with the effective ionpair inter� action considered within the framework of the nearly� freeelectron approximation based on the pseudopo� tential approach have actively been used for calculat� ing the thermodynamic properties of metal melts for many years (1-8). In this case, if model pseudo� potentials were used for these purposes in combination with various TPT methods (variational (1-6), Weeks- Chandler-Andersen (9) (WCA) (1, 2, 6, 7), and Barker-Henderson (2)), the firstprinciple ones were used only with the variational methods (3, 4, 8). In this study, together with the WCA method, we used the firstprinciple pseudopotential method (10) previously proposed by us, which enables us to con� sider a very wide circle of properties and gives good quantitative and qualitative results for simple metals and their alloys in the solid state (11). In this case, both the energy functions and their first and second deriva� tives agree well with the experimental data. Recently, this pseudopotential was used for calculating the thermodynamic properties of liquid alkali metals within the framework of the variational method (8). The Schrodinger pseudowave equation for con� duction electrons has the form ,( 1) where Hps and φk are called the pseudoHamiltonian acting on conduction electrons and their pseudowave functions, respectively; k is the conductionelectron state, is the pseudopotential acting on the elec� tron state k, and K is the kineticenergy operator. The transformation of the true Schrodinger equation into the pseudowave equation is exact, and the eigenval�