Electronic structure and magnetic interactions in LiV2O4

We present results of all-electron electronic structure calculations for th e recently discovered d electron heavy fermion compound LiV2O4. The augment ed spherical wave calculations are based on density functional theory withi n the local density approximation. The electronic properties near the Fermi energy originate almost exclusively from V 3d t(2g) states, which fall int o two equally occupied subbands: While sigma-type metal-metal bonding leads to rather broad bands, a small pi-type p-d overlap causes a narrow peak at E-F. Without the geometric frustration inherent in the crystal structure, spin-polarized calculations reveal an antiferromagnetic ground state and fe rromagnetic order at slightly higher energy. Since direct d-d exchange inte raction plays only a minor role, ordering of the localized vanadium moments can be attributed exclusively to a rather weak superexchange interaction. With the magnetic order suppressed by the geometric frustration, the remain ing spin fluctuations suggest an explanation of the low-temperature behavio ur of the specific heat.