Effect of isotope substitution on thermal expansion of LiH crystal

The isotope effect on the lattice parameter and the coefficient of thermal expansion of the LiH crystal is investigated by means of rigid-ion model. It is demonstrated that the differences in lattice parameters between LiH isotopes can be related directly to changes in the thermal-expansion coefficient which varies inversely as the cation-anion reduced mass. These differences should disappear at a temperature of 0 K. For the first time, the thermal-expansion data are calculated for the six isotopic components 6LiH, 7LiH, 6LiD, 7LiD, 6LiT, and 7LiT. The lattice parameters of LiH isotopes are also calculated and agree with those observed earlier within the experiment error. (orig.)