Two-dimensional folding technique for enhancing Fermi surface signatures in the momentum density: Application to Compton scattering data from an Al-3at. % Li disordered alloy - art. no. 045121

We present a technique for enhancing Fermi surface (FS) signatures in the t wo-dimensional (2D) distribution obtained after the 3D momentum density in a crystal is projected along a specific direction in momentum space. These results are useful for investigating fermiology via high-resolution Compton scattering and positron annihilation spectroscopies. We focus on the parti cular case of the (110) projection in a fcc crystal where the standard appr oach based on the use of the Lock-Crisp-West (LCW) folding theorem fails to give a clear FS image due to the strong overlap with FS images obtained th rough projection from higher Brillouin zones. We show how these superposed FS images can be disentangled by using a selected set of reciprocal lattice vectors in the folding process. The applicability of our partial folding s cheme is illustrated by considering Compton spectra from an Al-3 at. % Li d isordered alloy single crystal. For this purpose, high-resolution Compton p rofiles along nine directions in the (110) plane were measured. Correspondi ng highly accurate theoretical profiles in Al-3 at. % Li were computed with in the local density approximation (LDA)-based Korringa-Kohn-Rostoker coher ent potential approximation (KKR-CPA) first-principles framework. A good le vel of overall accord between theory and experiment is obtained, some expec ted discrepancies reflecting electron correlation effects notwithstanding, and the partial folding scheme is shown to yield a clear FS image in the (1 10) plane in Al-3 at. % Li.