关联电子系统的动力学CPA和紧束缚LMTO方法
Dynamical CPA and Tight-Binding LMTO Approach to Correlated Electron System
摘要：
将关联电子的动力学相干势近似（CPA）推广到由第一性原理紧束缚线性Muffintin轨道（LMTO）带和原子内库仑相互作用组成的具有真实哈密顿量的系统。基于泛函积分方法和忽略不同频率的动力学势之间模-模耦合的调和近似，得到了热力学势和格林函数的自洽方程。对Fe和Ni在静态近似下进行了二阶动力学修正的数值计算。在有限温度下，获得了Ni的准粒子态的能带变窄和6 eV卫星态。该理论得出了Fe和Ni的居里-韦斯定律。计算出的有效波尔磁子数对于Fe为3.0 $μ_{\rm B}$，对于Ni为1.2 $μ_{\rm B}$，解释了实验数据。但计算的居里温度为2020 K的Fe和1260 K的Ni，仍然高估了两倍的实验相比。通过与静态近似下的结果进行比较，讨论了动力学效应对电子和磁性的影响。
英文摘要：
Dynamical Coherent-Potential Approximation (CPA) to correlated electrons has been extended to a system with realistic Hamiltonian which consists of the first-principles tight-binding Linear Muffintin Orbital (LMTO) bands and intraatomic Coulomb interactions. Thermodynamic potential and self-consistent equations for Green function are obtained on the basis of the functional integral method and the harmonic approximation which neglects the mode-mode couplings between the dynamical potentials with different frequency. Numerical calculations have been performed for Fe and Ni within the 2nd-order dynamical corrections to the static approximation. The band narrowing of the quasiparticle states and the 6 eV satellite are obtained for Ni at finite temperatures. The theory leads to the Curie-Weiss law for both Fe and Ni. Calculated effective Bohr magneton numbers are 3.0 $μ_{\rm B}$ for Fe and 1.2 $μ_{\rm B}$ for Ni, explaining the experimental data. But calculated Curie temperatures are 2020 K for Fe and 1260 K for Ni, being still overestimated by a factor of two as compared with the experimental ones. Dynamical effects on electronic and magnetic properties are discussed by comparing with those in the static approximations.
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