THE SI-28 LATTICE-PARAMETER

Accurate measurements of the lattice parameter of a Si-28 enriched single crystal and the results of first-principle calculations of the dependence of the Si lattice parameter on temperature and on isotopic composition are reported. A comparison between theoretical and experimental results demonstrates the importance of the influence of impurities on the lattice parameter. When the latter effect is taken into account it follows that the isotopically enriched crystal's lattice parameter is about 2.10(-6) larger than that of a naturally composed Si crystal.