- The effective interaction potential for tungsten is used to calculate the second moment of phonon spectrum, , Debye temperature, and cohesive properties. It is shown that the potentials obtained give good agreement of cohesive properties with the data calculated from the universal function of Rose et al. The applicability of the atomic sphere approximation to the calculation of the integral thermodynamic properties of tungsten is discussed. The convergence of in real space is studied; we find that the main contribution to is given by the first coordination shell. The Gibbs–Bogoliubov inequality and the variational procedure of Ross are used to calculate the temperature dependence of free energy in liquid tungsten. The thermodynamic functions obtained for solid and liquid phases are employed in determination of the melting temperature. © 1995 John Wiley & Sons, Inc.