ZERO-POINT AND ISOTOPE SHIFTS - RELATION TO THERMAL SHIFTS

Zero-point motion of the atoms of a molecule or solid causes renormali zation of physical properties. This renormalization depends on the vib rational amplitudes and thus on the isotopic mass, giving rise to isot ope shifts of quantities such as bandgaps and lattice constants. This effect is normally omitted in bandstructure calculations. Therefore it is appropriate to compare theory not with experiment but rather with values which are corrected for zero-point renormalization. A simple sc heme is presented for doing this by linear extrapolation of high-T the rmal shift data back to T=0.