Influence of lattice dynamics on electron momentum density of lithium

Abstract

High resolution Compton profile measurements of single crystalline Li were performed for momentum transfer q → ∥[110] with 0.12 a.u. momentum space resolution at room temperature and at 95 K using the Compton spectrometer of ID 15 B at ESRF. The valence electron Compton profile at 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 account when calculating the Fermi energy and Fourier coefficients of the empirical pseudopotential are multiplied by the corresponding Debye–Waller factor to simulate the thermal disorder. Thus the measured temperature effect can be traced back not only to the variation of the lattice constant with temperature but also to the decreasing contributions of higher momentum components to the total momentum density with increasing temperature.