The Theoretical Study On CH₃OH(H₂O)n By AB INITIO Method

The interaction energy and geometries of the complexes involving water,methanol and ethanol are systematical studied by using the Ab initio(HF,B3LYP MP2/sto-3g,3-21g,6-31g,6-311+g(d,p)) theoretical,these Include the heterodimersobtained from water-methanol,water-ethanol,methanol-ethanol,Configurations of the clusters are full optimized,it is shown that the first stationary structure is linear hydrogen bonding dimer water,methanol and water,ethanol and water in clusters.,Second-order Moller-plesset MP2/6-311+g(d,p) calculations were performed to obtain the interaction energy and configurations of the complexes involving water,methanol and ethanol. Some Forcefield such as cvff,esff,cff91 and amber were studied by calculating the interaction energy and configuration. It is confirmed that there are 2 heterodimer CH₃OH(H₂O) and It is presumed that there are respectively 8 cyclic trimer and 16 cyclic tetramer when CH3OH combines water from two to three .Rotational constants(MHz) of methanol-water heterodimers and methanol(water)2 trimer obtained at the MP2/6-311+g(d,p) level ,Harmonic vibrational frequencies of methanol-water dimer and methanol(water)2 trimer .Values obtained at the B3LYP/6-311+g(d,p) level; Values of the isotropic and anisotropic chemical shifts for MeW complex(in ppm),using two theoretical models.We could not find experimental information in the literature regarding the methanol(water)2 cluster ,and We could not find revelence information in the literature after CH3OH combines water From 4 to 6. present work is just reference for the future. Considering the energy obtained at the MP2/6-31 l+g(d,p) level,the structure of cyclic is lower ,due to the cooperative effects.