AB Initio Study Of Ground State And Low Excited State Of NH,CH,OH Molecule

The potential energy function of atomic molecules obtained by solving the equation of electron motion is very important for studying the properties of diatomic molecules.On the one hand,molecular potential energy function has a very close relationship with quantum mechanics theory,molecular structure and molecular spectrum,atomic molecular group theory,atomic molecule collision and the reaction Kinetics.On the other hand,the molecular potential energy function can fully describe the energy,geometry,mechanics and spectral properties of the molecule in the whole space.Based on this,the molecular potential energy function has always been a hot topic in the field of atomic molecules.The potential energy function,spectral constant and vibrational energy level of the ground state and excited state of NH,CH and OH molecules were studied by ab initio method.First: the ab initio study of the ground state and excited state of NH molecules.The single-point energy scan of the ground and excited states of the NH molecule was performed using the CCSD(T)method in the coupled cluster theory combined with the cc-pv5 z basis set and the QCISD(T)method combined with the aug-cc-pvqz basis set.The result is fitted to the potential energy function.The potential energy function is used to find the spectral constants of the ground state and the excited state of the NH molecule.By solving the radial Schr?dinger equation,all reasonable vibrational dynamics of the ground state and the excited state of the NH molecule at the rotational quantum number J=0 are found.And calculate the vibration level,inertial rotation constant and centrifugal distortion constant of each state.Second: the ab initio study of the ground state and excited state of CH molecule.Using the CCSD(T)method in the coupled cluster theory and the cc-pv5 z and aug-cc-pvqz basis sets,the ab initio calculations of the ground and excited states of CH molecules were carried out,and the potential energy functions of the ground and excited states of CH were obtained.Then,the potential constant function is used to solve the spectral constants of the ground state and the excited state of the CH molecule.The radial Schr?dinger equation is solved based on the potential energy function,and the vibrational dynamics of the ground state and the excited state of the CH molecule at the rotational quantum number J=0 are obtained.Vibrational vibration levels and centrifugal distortion are common.Third: the ab initio study of the ground state and excited state properties of OH molecules.Using the CCSD(T)method in the coupled cluster theory combined with the cc-pv5 z basis set and the B3 LYP functional and the aug-cc-pv5 z basis set in the density functional theory,the single-point energy scan of the ground state and the excited state of the OH molecule,respectively,will be performed.The results of the scan are fitted to the potential energy function.On the basis of the potential energy function,the spectral constants of each state of the OH molecule are calculated.By solving the radial Schr?dinger equation,the energy levels,inertial rotation constants and centrifugal distortion constants of each vibration are obtained.