The Study Of Radical OH Using Gaussian

Transient molecules are short-lived species, which often exist as intermediates of chemical, physical and biological processes. They are the keys for deep understanding of chemical dynamics and molecule structure. OH as one of the few special and relatively stable free radical, has always been of interest to physicists and chemists, and has been investigated both extensively and intensively.Here the ground state and excited state of OH are studied by GAUSSIAN software. For the ground state, The potential energy is calculated with the DFT method B3PW91 and basis set 6-311++G(3df,3pd). The vibrational and rotational constants are obtained by solving the schodinger's equation with the calculated potential energy. They are good enough to compare with experimental values. For the excited state, the potential energy is obtained with CASSCF method and basis set 6-311++G(3df,3pd). The calculated equilibrium position is in good agreement with the experimental value. The error of the adiabatic excited energy is 0.52eV. Both calculated potential energy curves of ground and excited states are in good greement with RKR potential curve which is based on the experimental ro-vibrational constants.In addition, Amplitude modulation of the twisted nematic liquid crystal display was introduced briefly.