Center for Functional Nanomaterials Seminar

Center for Functional Nanomaterials Seminar Wave functions in reduced density matrix functional theory Hubertus Van Dam (BNL) Friday, November 20, 2015 2:00 p.m. Bldg. 735 â€" Conf. Rm. A Abstract: Reduced density matrix theories are an answer to the problem of dealing with the complexity of wave functions, originally in particular the full-CI wave function. The objective to eliminate the wave function altogether and replace it with a reduced density matrix led to the search for N-representability conditions. For the one-electron density matrix the N-representability conditions were proven by Coleman in 1963. For the two-matrix they were proven by Mazzotti in 2012, but require a hierarchy of density matrices all the way to the full-CI density matrix. The latter causes practical difficulties that require approximations to overcome them. As a response one may ask: what if a compact wave function could be formulated that generates the correct density matrix up to a pre-selected order while requiring a data complexity that is of the same order as the density matrix? In this talk I will show that for the one-electron density matrix a single determinant wave function can be formulated that can represent any arbitrary one-electron density matrix. Incidentally this wave function is also the exact Kohn-Sham system in contrast to the wave function conventionally used in density functional theory. Host: Qin Wu