| Research Abstract |
Electronic vand strucurures and total energies are calculated for intercalated compounds A_xTiS_2 (A = transition-metals, silver, and alkaline metals) and trnary intermetallic compounds Mn_2Sb, Mn_3GaC, and Fe_7Se_8 by using the LAPW method.
1. A_xTiS_2 (A = transition-metals, silver, and alkaline metals) For the silver-intercalated compound Ag_x TiS_2 the selectronic states of silver atoms hybridize strongly with those of the host material, but a cohesive energy gain due to the hybrideization is rather small. On the other hand, the alkaline metal atoms only donate electrons to the host material. The chemical bonds between guest atoms and the host material are relatively weak for Ag_xTiS_2 and the alkline-metal-intercalated compounds compared with the transition-metal-intercalated compounds. From the total energy calculation it is confirmed that the ABC-stacking structure is more stable than the AB-stacking is favorable for Ag_xTiS_2.
2. Ternary intermetallic compounds Mn_2Sb, Mn_3GaC, and Fe_7Se_8 (1) Mn_2Sb : From the total energies calculated as a function of the lattice constants, a and c, it is found that the ferrimagnetic state is more stable than the antiferromagnetic state. The evaluated value of the linear compressibility along the a-axis is larger than that along the c-axis. (2) Mn_3GaC : It is found that both the magnitude of the magnetic moment at each maganese site and its volume dependence are larger for the antiferromagnetic state than those for the ferromagnetic state. Further, the antiferromagnetic phase becomes more stable than the ferromagneric state in larger volume side. (39 Fe_7Se_8 : In the ferrimagnetic state, the magnetic moments at crystallographically inequivalent iron sites have almost the same values with each other. The photoemission and the optical conductivity spectra clculated from the electronic density of states are in good correspondence with the observations.
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