2005/08/16 by I. Leonov, A. N. Yaresko, V. N. Antonov +6 · 1 citation
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Crystal Structures and Properties #Magnetic and transport properties of perovskites and related materials #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1088/0953-8984/18/48/022
published as J. Phys.: Condens. Matter 18, 10955-10964 (2006) · 6 pages, 4 figures
arxiv created 2005/08/16 · openalex publication_date 2006/11/17 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
Charge ordering in the low-temperature triclinic structure of titanium oxide (Ti 4 O 7 ) is investigated using the local density approximation (LDA)+ U method. Although the total 3d charge separation is rather small, an orbital order parameter defined as the difference between t 2g occupancies of Ti 3+ and Ti 4+ cations is large and gives direct evidence for charge ordering. Strong covalency of O 2p–Ti 3d σ-type bonds, which results in partial occupation of Ti e g states, leads to almost complete loss of the disproportionation between the charges at 3+ and 4+ Ti sites. The occupied t 2g states of Ti 3+ cations are predominantly of d xy character and form a spin-singlet molecular orbital via strong direct antiferromagnetic exchange coupling between neighbouring Ti(1) and Ti(3) sites, whereas the role of superexchange is found to be negligible.