Communication: Proper use of broken-symmetry calculations in antiferromagnetic polyradicals

J Chem Phys. 2016 Jun 7;144(21):211101. doi: 10.1063/1.4953040.

Abstract

The present comment formulates some recommendations regarding the use of broken-symmetry Unrestricted Density Functional Theory (UDFT) solutions in those polyradical architectures predicted to be of ground-state singlet character according to Ovchinnikov's rule. It proposes a procedure to identify the number of open shells, to reach the relevant Ms = 0 solution, and to estimate the low-energy spectrum of the states which keeps this number of open shells.