Calculation of Compton profiles and positron annihilation matrix elements using LMTO wavefunctions

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Abstract
The linear muffin-tin orbital (LMTO) band method is used to calculate the electronic structure and the matrix elements for electron momentum distributions (EMD) and two-photon momentum distributions (TPMD) for use in calculations of Compton profile and positron annihilation experiments, respectively. The results are satisfactory for the first Brillouin zone (BZ) even when no corrections to the overlapping sphere geometry are made. However, an efficient method to correct for the overlapping spheres is derived and is shown to produce excellent results for Umklapp processes also. This makes the LMTO wavefunctions as accurate as the wavefunctions obtained from more costly band methods. Examples are given for alkali metals and vanadium, for which comparison with other calculations are made.