N. Helbig et al 2007 EPL 77 67003 doi:10.1209/0295-5075/77/67003
N. Helbig1,2, N. N. Lathiotakis1, M. Albrecht3 and E. K. U. Gross1
Show affiliationsWe present a novel method for calculating the fundamental gap. To this end, reduced-density-matrix-functional theory is generalized to fractional particle number. For each fixed particle number, M, the total energy is minimized with respect to the natural orbitals and their occupation numbers. This leads to a function, EtotM, whose derivative with respect to the particle number has a discontinuity identical to the gap. In contrast to density functional theory, the energy minimum is generally not a stationary point of the total-energy functional. Numerical results, presented for alkali atoms, the LiH molecule, the periodic one-dimensional LiH chain, and solid Ne, are in excellent agreement with CI calculations and/or experimental data.
71.10.-w Theories and models of many-electron systems
31.10.+z Theory of electronic structure, electronic transitions, and chemical binding
Issue 6 (March 2007)
Received 10 October 2006, in final form 2 February 2007
Published 2 March 2007
N. Helbig et al 2007 EPL 77 67003
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