重费米子化合物LiV2 O4电子结构的第一性原理研究

用第一性原理的FP-LMTO能带计算方法研究了重费米子化合物LiV2O4的电子结构.结果表明:费米面附近的导带是由V原子的3d电子形成的宽度为2.5eV的窄能带,是3d态在立方晶体场中具有t2g对称性的子带;它与O的2p轨道构成的能带有近1.9eV的能隙.计算得出的费米能处电子态密度和线性电子比热系数分别是11.1 states/eV f.u.和26.7 mJ/molK2.费米面处的能带色散具有电子型和空穴型两种,呈现出一种复杂的费米面结构.LSDA以及LDA+GGA计算表明, LiV2O4有一个磁矩为每个钒原子1.13μB,总能比LDA基态低约148 meV/f.u.的铁磁性基态.由目前的能带结构计算的结果无法确定这一类Kondo体系的局域磁矩的来源,表明这一化合物中的重费米子行为可能有别于在含有4f和5f稀土的重费米子合金中观察到的局域磁矩与传导电子的交换作用机制,其中存在量子相变的可能.

Ab initio Electronic Structure Study for Heavy Fermion Spinel LiV2 O4

We preformed a self-consistent full-potential LMTO LDA calculation for heavy fermion compoundsLiV2O4. The present results show that the conduction bands in this compound are formed from V 3dstateswith abandwidthof 2.5 eV. Thesymmetric charactersof conduction bandsareof t2gin principle. The energy gap between conduction bands and fully occupied O2p bands is 1.9 eV. The band dispersions near Fermi energy display complicated structures. Furthermore, theN(EF) andγare 11.1states/eVf.u. and 26.7 mJ/molK2determined numerically by LDA calculation, respectively. It is insufficient to clarify the origin of local moment in LiV2O4from plain LDA calculations. In addition to the above LDA calculation, we also find a LSDAsolution of LiV2O4that is lower in total energy than that of LDA calculation. Similarly, LSDA+GGA calculation yields almost the same results as that in LSDA. It is concluded that the mechanism responsible for heavy fermion properties in LiV2O4might be some what different from the plain Kondo mechanism in conventional 4f and 5f heavy fermion compounds and perhaps the quantum transition plays an adequate role to heavy fermion behavior in LiV2O4.