Acta Physica Academiae Scientiarum Hungaricae 30. (1971)
1971 / 2. szám - T. Siklós: Theory of Anharmonic Crystals in Pseudoharmonic Approximation II. Three-Dimensional Lattice
198 T. SIKLÓS For the values of A ]> 12 we obtain the following values for the critical temperature T* ^ 1.56 and the critical pressure P* 0.37 where T* = = 0/g = 11.76 t/A is the reduced temperature. The following expressions were obtained in [2] for the instability temperature* for high (r 1) and low (r 1) temperatures: Fig. 2. The dependence of the instability temperature rf = &sl0,oL on the dimensionless coupling constant A of the atoms T, = 1,02A 3e |1 + 17 P* 24 1,02 A (19) (т>1; P*< 1) 1,05 Í 10 ne 3e 1/4 ; A0 = — J1 — 2 1 7,12 e~(20) (r <1; P* <? 1) * We note here that in [2] the instability temperature was called the critical temperature and denoted byc r. Acta Physica Academiae Scientiarum Hungaricae 30, 1971