Challenges for semilocal density functionals with asymptotically nonvanishing potentials

Abstract

The Becke-Johnson model potential [A. D. Becke and E. R. Johnson, J. Chem. Phys. 124, 221101 (2006)JCPSA60021-960610.1063/1.2213970] and the potential of the AK13 functional [R. Armiento and S. Kümmel, Phys. Rev. Lett. 111, 036402 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.036402] have been shown to mimic features of the exact Kohn-Sham exchange potential, such as step structures that are associated with shell closings and particle-number changes. A key element in the construction of these functionals is that the potential has a limiting value far outside a finite system that is a system-dependent constant rather than zero. We discuss a set of anomalous features in these functionals that are closely connected to the nonvanishing asymptotic potential. The findings constitute a formidable challenge for the future development of semilocal functionals based on the concept of a nonvanishing asymptotic constant.