Simplified computations of spin excitations in high-spin carbon nanoclusters and related systems

Abstract

Spin excitation spectra for possible molecule-based magnetic structures are evaluated semiempirically. A simplest spin-flip model with singly-excited configurations (SF-CIS) is used. While only a small amount of electron correlation is captured by the SF-CIS scheme, it turns out to be practically useful tool for computing quasi-magnon spectra in large polyradicals. We study examples of three different structural types (graphene nanoribbon with methylene edges, triangulene and Mataga-type model organic ferromagnet). We demonstrate that these systems show different behavior of the spin excitation spectra and different spin heat capacity temperature dependences. It is also shown that the same SF-CIS technique can be useful for describing high-spin states in nanodiamonds with defects.