The upper critical field of clean MgB2 is investigated using the two-band layered Ginzburg-Landau （GL） theory. The calculated results are fitted to the experimental data of clean MgB2 crystal very well in a broad temperature range. Based on the GL theory for clean superconductors, a phenomenological theory for dirty superconductor is proposed. Selecting appropriate parameters, two-band layered GL theory is successfully applied to the crystal of Mg（B1-xCx）2 and the neutron irradiation samples of MgB2.
The crystal structure stability as well as electric conductance of (Sr/Ca)_2CuO_2Cl_2 compound with K_2NiF_4 structure was investigated up to 31 GPa using diamond anvil technique. It seems that (Sr/Ca)_2CuO_2Cl_2 is quite stable under pressure but with obvious anisotropic compressibility. The equation of state (EOS) obtained shows relative large bulk modulus.
LIU QingQingWANG FuRenLI FengYingCHEN LiangChenYU RiChengJIN ChangQingLI YanChunLIU Jing
