Li Le-Min

Study on Band Structure of YbB6 and Analysis of Its Optical Conductivity Spectrum

Abstract The electronic structure of YbB6 crystal was studied by means of density functional (GGA + U) method. The calculations were performed by FLAPW method. The high accurate band structure was achieved. The correlation between the feature of the band structure and the Yb-B6 bonding in YbB6 was analyzed. On this basis, some optical constants of YbB6 such as reflectivity, dielectric function, optical conductivity, and energy-loss function were calculated. The results are in good agreement with the experiments. The real part of the optical conductivity spectrum and the energy-loss function spectrum were analyzed in detail. The assignments of the spectra were carried out to correlate the spectral peaks with the interband electronic transitions, which justify the reasonable part of previous empirical assignments and renew the missed or incorrect ones.

FT-IR Study And Intensity Calculation On The Hydration Of Acetonitrile

During recent years, the FT-IR study on hydration of molecules attracted considerable interests. The peak positions and intensities of IR bands of some molecules change apparently after hydration. The theoretical explanation to these changes, especially to the intensity variation, is rather few. In this investigation, the effect of hydration on the IR intensity of acetonitrile has been systematically studied. Three parts are included: 1. Experiments: CH3CN-CC14-H20 systems were prepared from acetonitrile, tetrachloromethane and water. The volume percents of acetonitrile kept 80% in all solutions and the volumes of water in these solutions were 0.0, 3.0, 6.0, 9.0, 12.0 and 15.0% respectively. The infrared spectra of these solutions were measured quantitatively by Nicolet 7199B FT-IR spectrometer. It was found that the intensity of C-N stretching band(2200 cm-1) became stronger when water was added and the more the water was added, the larger the intensity increase was. This is caused by the formation of hydrogen bond between CH3CN and H20. 2. Normal coordinate analysis: The normal analysis of CH3CN was carried out. It was found that the IR spectrum of liquid acetonitrile could not be explained by the model of C3v symmetry of acetonitrile molecule. This effect on the IR bands is now under investigation. 3. The infrared intensity calculation: The atomic polar tensors (APT s) of CH3CN and CH3CN--H20 were calculated. The APIs of CH3CN were quite different from those of CH3CN--H20. The infrared intensities of C-N stretching bands in CH3CN and CH3CN--H20 were calculated respectively. The increase of IR intensity of C--N stretching band when water was added has been explained to some extent.