任意電子密度兩原子哈伯模式的費米能階及磁感性

Abstract

The eigenvalue problem of a two-site Hubbard Hamiltonian, which contains sboth the correlation term U and the hopping term t , is solved exactly and the grand partition function of the system is obtained. The chemical potential as a function of temperature for a given number of electrons per site n is numerically calculated for several values of n.The chemical potential as a function of n at absolute zero is shown to have three discontinuouties at n=1/2,1,and 3/2. The magnetic suspectibility per site is shown to be of the Curie-Weiss form for the temperature range t<<kT<<U. Both the Curie constant and the Weiss temperature are proportional to n (if 0<n≦1) or ti (2-n) (if 1<n≦2). The Curie constant is independent of any parameter of the model and would predict n=0.27 for N-methyl-phenazinium-tetracyanoquiodimethane (NMP-TCNQ) which is not close to the experimental value of n=0.9.