No abstract

An equation of state for metals is obtained by assuming that the electronic free energy varies very slowly with volume. In this derivation, the static contribution of the lattice to the free energy is based upon the LJD potential while the lattice vibrations are considered in the harmonic approximation. The theoretical results are compared with experiment for copper with respect to thermal expansion, and good agreement in the temperature range 20–600 K is obtained. For the isothermal variation of volume with pressure, the theory is found to be in agreement with experiment up to 25 000 kg/cm2.

An equation of state for metals based upon a simple model, which ignores the effect of free electrons, was given in an earlier paper. An improved equation of state is obtained for monovalent metals by taking account of the electronic contribution in the free energy expression. This result is used to explain the thermal expansivity of copper in the range between 1 and 12 K. The same set of parameters give theoretical specific heat values which are in fairly good agreement with the reported experimental data in the same range of temperature.

An equation of state for metals based on a simple model was obtained in an e a r l i e r paper /1/ and applied to explain the observed thermal expansivity of copper by Hahn /2/ over a very wide range of temperatures. It was found that this theory could correctly describe the volume changes on compression for this metal a t room temperature up to 25 kbar. The object of this communication is to report results of s i m i l a r comparisons for lead, aluminium, silver, nickel, and gold. All these metals like copper possess f.c.c. crystal structure so that no changes in the numerical constants occurring in the expression for the lattice intesaction free energy need to be made.AS shown in the e a r l i e r paper, t h e atmospheric pressure thermal expansivity CL: using the Debye approximation i s given effectively by the expression C ( X ) 4 a = 223