Electronic and magnetic properties of the different phases of Ti4 O7 from density functional theory

MARIANA WEISSMANN; RUBEN WEHT

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Año: 2011 vol. 84 p. 44191 - 44194

1098-0121

Ab initio calculations using the local spin-density approximation plus Hubbard U (LSDA+U) method have been performed for the three reported phases of Ti4 O7 . Using the experimental structural parameters, we find that the electronic and magnetic properties are qualitatively different for each phase. The low-temperature structure is an antiferromagnetic semiconductor, with bipolarons arranged symmetrically in chains, separated by other nonmagnetic ion chains. The intermediate-temperature structure also contains bipolarons, but in a much more complicated order, in addition to unpaired magnetic Ti3+ ions and nonmagnetic Ti4+ ions. It has a smaller band gap than the low-temperature one. The high-temperature structure is metallic, and different distributions of Ti3+ and Ti4+ ions can be found that are almost degenerate.