Mode Gruneisen parameters in potassium. I

Abstract

The normal mode Gruneisen gamma parameters have been measured for several modes of vibration of potassium at 4.5K over the pressure range 0.001 to 4.1 kbar, by means of coherent inelastic neutron scattering experiments. The results are compared with six different theoretical calculations based on a variety of screened pseudopotential models for the interionic forces in this simple metal, including a very recent calculation described in the following paper by Taylor and Glyde (ibid., vol.6, no.10, p.1915 (1976)). There is overall qualitative agreement between several theories and experiment, but significant discrepancies exist for four particular normal modes. Significant differences are also found between the present results for certain low frequency transverse modes and the analogous gamma values derived from the pressure dependence of the elastic constant C₄₄ at room temperature.