Inter-atomic Force Law and Equation of State of Solids

The pressure of a solid has been divided into two terms p 1 and p 2 , of which the first is the static part due to a non-vibrating lattice at T = 0, and the second arises from the thermal vibrations. For all volumes measured at zero pressure the two are equal and opposite to each other. The static pressures of eight solid elements, aluminium, copper, silver, gold, lead, platinum, tungsten and molybdenum, have been obtained from their thermal pressures γ E / V by the use of the above condition. The average Gruneisen constant γ has been calculated in the usual way from the thermal expansion and the specific heat data. These static pressures have been compared with the derivatives of the potential energy as derived from the inter-atomic potential used earlier by Furth, and a very close agreement has been observed between them.