Spectral density and metal-insulator phase transition in Mott insulators   within RDMFT
  We present a method for calculating the spectrum of periodic solids within reduced density matrix functional theory. This method is validated by a detailed comparison of the angular momentum projected spectral density with that of well established many-body techniques, in all cases finding an excellent agreement. The physics behind the pressure induced insulator-metal phase transition in MnO is investigated. The driving mechanism of this transition is identified as increased crystal field splitting with pressure, resulting in a charge redistribution between the Mn $e_g$ and $t_2g$ symmetry projected states. 
S. Sharma, J. K. Dewhurst, S. Shallcross, E. K. U. Gross
cond-mat.str-el cond-mat.mtrl-sci