Influence of lattice dynamics on electron momentum density of lithium

High resolution Compton profile measurements of single crystalline Li were performed for momentum transfer (q) over bar parallel to [110] with 0.12 a, u. momentum space resolution at room temperature and at 95 K using the Comp ton spectrometer of ID 15 B at ESRF. The valence electron Compton profile a t room temperature is higher around p(z) = 0 a.u. and lower for \p(z)\ > 0. 4 a.u. when compared with the one at 95 K. The experimental results are in good agreement with calculations using an empirical pseudopotential scheme, where the variation of lattice constant with temperature is taken into acc ount when calculating the Fermi energy and Fourier coefficients of the empi rical pseudopotential are multiplied by the corresponding Debye-Waller fact or to simulate the thermal disorder. Thus the measured temperature effect c an be traced back not only to the variation of the lattice constant with te mperature but also to the decreasing contributions of higher momentum compo nents to the total momentum density with increasing temperature. (C) 2000 E lsevier Science Ltd. All rights reserved.