The Key role of vibrational entropy in the phase transitions of dithiazolyl-based bistable magnetic materials

Vela, S.*; Mota, F.*; Deumal, M.*; Suizu, Rie*; Shuku, Yoshiaki*; Mizuno, Asato*; Awaga, Kunio*; Shiga, Motoyuki   ; Novoa, J.*; Ribas-Arino, J.*

Recent years have witnessed a growing interest in the use of organic radicals as building blocks for bistable materials, i.e. materials that exist in two inter-exchangeable phases under identical thermodynamic conditions. The neutral radical TTTA is a prominent dithiazolyl-based compound because of its spin transition with a hysterisis nature near the room temperature. From ab initio molecular dynamics simulations, it has been evident that this phase transition is driven by the pair exchange dynamics of molecular stacking units accompanied by a significant gain of vibrational entropy.