First-Principles Study on the Stability and Electronic Structure of the Charge-Ordered Phase in α-(BEDT-TTF)2I3

Abstract

We theoretically study the structural and electronic properties of a molecular conductor, α-(BEDT-TTF)2I3, using first-principles density-functional theory calculations, especially in its low-temperature charge-ordered state at ambient pressure. We apply a hybrid functional approach and compare the results with a conventional exchange-correlation functional within the generalized gradient approximation. By performing structural optimization, we found a stable charge-ordered solution for the former, in contrast to the latter approach where the magnitude of the charge imbalance becomes considerably small compared to that when the experimental structure is adopted. The electronic band structure near the Fermi level, with and without structural optimization, as well as the molecule-dependent local density of states of the charge-ordered state are discussed.