| There are two sections in this dissertation. Firstly, the intermolecular hydrogen-bonding interactions in water/methanol mixed solvent have been investigated by using quantum mechanics method. In the other section, a set of new nonequilibrium solvation theories have been introduced on the basis of continuum model. Accordingly the expressions of solvation electrostatic free energy, solvent reorganization energy and spectral shift have been reformulated. Based on the new theory, a procedure for spectral shift has been developed, and the codes for solvent reorganization energy calculations have been implemented in quantum computational packages. All of the examples show that the results of our theoretical calculations are consistent with the experiments.In the first chapter, the hydrogen-bonding structures of water-methanol mixed solvent have been elaborately investigated. By using density functional theory, the structures of some clusters in the mixed solvent have been optimized at B3LYP/6-31G* level, and the single-point calculations have been done at B3LYP/6-31+G* level. By means of the analysis of the conformations and the vibration frequencies, the five- and six-member cyclic structures are found to be the most stable among all kinds of the water clusters. Furthermore, we discovered a novel feather that a methanol molecule can form very stable double-hydrogen bonding with the cyclic structures. According to the stabilization energies of these intermolecular interactions, the effects of water-methanol solvent on the solubility of the PNIPAM have been discussed. A reasonable explanation for the experimental phenomena has been put forward.In the second chapter, the candidate introduces the progresses of the laboratory in the area of nonequilibrium solvation theory. At first the background of the classical solvation theory has been introduced, and some problems in the presentsolvation theory have been pointed out. On the basis of continuum model, starting from the formula of fundamental electrodynamics, we put forward a set of nonequilibrium solvation theory through severe deduction. The new theory is quite different from the previous ones, because the latter thought that there is self-energy in the polarized solvent, while we have confirmed that the so-called 'self-energy' is equal to zero. Consequently our expressions for spectral shift of electronic absorption spectrum and solvent reorganization energy of electron transfer are quite distinct from previous ones.Before this work, a procedure has been developed based on multipole expansion method to calculate spectral shift. In the third chapter, the super-molecule method has been introduced to describe the hydrogen bonding and the dispersion interactions. Combining with the procedure, the photoionization process of nitrate anion has been investigated to check the new theory. The results of our theoretical calculations are consistent with the experimental value. The main part of the spectral shift attributes to the hydrogen bonding interaction.Another way to obtain nonequilibrium solvation energy is to directly work out the Poisson equation. In the last chapter, the COSMO module in Hondo99 package has been modified to calculate the solvent reorganization energy of electron transfer reactions. The original files have been compiled and linked under Windows. Linux and Aix circumstance, and the program can run in the three systems. A special example. He-He+ self-exchange electron transfer, has been employed to verify if the modified program is consistent with the new theory. Then in order to confirm the validation of our new theory, the trans-biphenyl-cyclohexane-naphthalene electron transfer system has been investigated by using the modified program. The results of theoretical calculations for solvent reorganization energy is compared with the experiment values obtained by Miller et al.. The modified program for solvent reorganization energy calculations provides a powerful tool for the application of our new theory.
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