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LXXX. A note on the interatomic and lattice potentials in solid helium

1955; Taylor & Francis; Volume: 46; Issue: 378 Linguagem: Inglês

10.1080/14786440708520597

1941-5990

D. J. Hooton,

Spacecraft and Cryogenic Technologies

Summary The interatomic potential φ(r) has been recently re-determined from gaseous data by Yntema and Schneider (1950) and by Mason and Rice (1954). In this determination the main significance comes from smaller values of r than are encountered in lattice dynamics ; the same may be said for the simpler Lennard-Jones approximations, which have also been put forward at various times. It is suggested here that, for the purposes of lattice theory, a better approximation would be to choose a Lennard-Jones potential by directly fitting it, within the crystal range of r, to the most accurate gaseous estimate of φ (r) available. In illustration, a comparison of some quantities relevant to lattice dynamics is given for Yntema and Schneider's curve, and for a 6–12 Lennard-Jones potential fitted to it in this way. The characteristics of several recent or well-known estimates of φ(r) are tabulated, and the lattice potential Φ is calculated from the more important of them. The equivalence of the cubic and hexagonal closepacked structures is demonstrafed, and its physical significance for helium is discussed.