Charge Density Wave States and Structural Transition in Layered Chalcogenide TaSe_(2-x)Te_x

The structural features and three-dimensional nature of the charge density wave （CDW） state of the layered chalcogenide 1T-TaSe2-xTex （0≤x≤2.0） are characterized by Cs-corrected transmission electron microscopy measurements. Notable changes of both average structure and the CDW state arising from Te substitution for Se are clearly demonstrated in samples with x〉0.3. The commensurate CDW state characterized by the known star-of-David clustering in the 1T-TaSe2 crystal becomes visibly unstable with Te substitution and vanishes when x=0.3. The 1T-TaSe2-xTex （0.3≤x≤1.3） samples generally adopt a remarkable incommensurate CDW state with monoclinic distortion, which could be fundamentally in correlation with the strong qq-dependent electron-phonon coupling-induced period-lattice-distortion as identified in TaTe22. Systematic analysis demonstrates that the occurrence of superconductivity is related to the suppression of the commensurate CDW phase and the presence of discommensuration is an evident structural feature observed in the superconducting samples.

AIM Study on the Reaction of CH2SH Radical with Fluorine Atom

The reaction of CH2SH radical with fluorine atom was studied at the levels of B3LYP/6-311G（d,p） and MP2（Full）/6-311G（d,p）. The computational results show that the reaction has three channels and proceeds by the addition of fluorine atoms on carbon or sulfur sites of CH2SH, forming initial intermediates. The calculated results show that the channel, in which fluorine attaches to the carbon atom to form CH2S and HF, is the most likely reaction pathway. Topological analysis of electron density was carried out for the three channels. The change trends of the chemical bonds on the reaction paths were discussed. The energy transition states and the structure transition regions （states） of the three channels were found. The calculated results show that the structure transition regions are broad in unobvious exothermic reactions or unobvious endothermic reactions, and are narrow in obvious exothermic reactions or obvious endothermic reactions.

AIM Study on Reaction HNCX→HXCN （X=O, S and Se）

The reactions of HNCO to HOCN, HNCS to HSCN and HNCSe to HSeCN have been studied at MP2/6-311 ＋ ＋ G（2df, pd）//B3LYP/6-311 ＋ ＋G（2df, pd） level. Geometries of the reactants, transition states and products have been optimized and geometries of the transition states are reported for the first time. The reasons why HNCO and HNCS instead of HOCN and HSCN were easily detected have been explained. It was predicted that HNCSe will be more easily detected than HSeCN. The breakage and formation of the chemical bonds in the reactions have been discussed by the topological analysis method of electronic density. The calculated results show that there are two kinds of structure transition states （STS） in reactions studied.