Calculation and analysis of electronic structure. See research statement for details.

Compton profiles give unparalleled insight into the ground state interacting many body wave function. A many particle system is completely described by its many-particle density matrix. For the kinetic and external potential energies, as well as for all other one-particle properties, the reduced one-particle density matrix (1-RDM) is, in fact, sufficient. In order to treat strong correlations in a fully ab-initio manner, reduced density matrix functional theory (RDMFT) has recently been extended to fully non-collinear spins and to periodic solids. A new XC functional capable of treating extended solids and small finite systems equally well has also been designed by the Gross Group in Halle. We have recently incorporated electron momentum density calculation into the ELK code and this project, in conjunction with the Halle group, is to develop the ability to compute RDMFT electron momentum densities and Compton profiles. It should be emphasised that the Kohn-Sham orbitals of density functional theory are chosen to reproduce the ground state density in real space, not in momentum space. In RDMFT, the natural orbitals and occupation numbers (coming from the diagonalisation of the reduced density matrix) should give the correct density in momentum space, too. By measuring high quality Compton profiles in both a magnetic insulator and a correlated paramagnetic metal, it will then be possibly to both benchmark the RDMFT and develop a magnetic functional for RDMFT