Vector Charge Density Wave Model of Metallic and Trigonal Te

High pressure metallic (m-) Te and pressure dependence of trigonal (t-) Te are studied by the vector charge density wave (VCDW) model, namely by coupled CDWs on vector p orbitals. Metallic Te comprising dimerized zigzag chains as well as semiconducting t-Te with helical chains can be described by VCDWs with the wave numbers (0, π/2, π/2) and (2π/3, 2π/3, 2π/3), respectively, on a simple cubic lattice. The VCDW model is improved to include all the first order change of the transfer interaction so that the effect of shear deformation can be taken into account. The VCDW model with suitable parameters can describe the electronic and lattice structures of t-Te and most of their pressure dependences. It can qualitatively explain the characteristic features of m-Te such as the chain dimerization and anisotropic energy band. The difference in the free energies between m- and t-Te decreases by pressure explaining qualitatively the pressure induced semiconductor-metal and t-Te decreases by pressure explaining qualitatively the pressure induced semiconductor-metal transition.