外电场作用下水分子结构和电子光谱

采用密度泛函B3P86方法在aug—cc—pvqz基组水平上优化得到了在不同外电场（-0．06-0．05a．u．）作用下，水分子的基态电子状态、几何结构、电偶极矩和分子总能量。在优化构型下利用杂化CIS-DFT方法（CIS-B3P86）研究了同样外电场条件下对水分子的激发能和振子强度的影响。计算结果表明，基态分子几何构型与电场大小呈现强烈的依赖关系，分子偶极矩m随电场的增加而减小。分子总能量随着电场增加而降低。无论是正向还是反向外电场作用下，激发能随电场增加而减小，表明在外电场作用下，分子易于激发和离解。

Structure and electronic spectrum for water molecule under the external electric field

The ground states of water molecule under different intense electric fields ranging from -0.06 to 0.05 a.u are optimized using density functional theory DFT/B3P86 at aug-cc-pvqz basis set level. The excitation energies and oscillator strengths under the same intense applied electric fields are calculated employing the revised hybrid CIS-DFT method. The results show that the electronic state,molecular geometry,total energy,dipole moment,and excitation energy are strongly dependent on the applied electric field. As the electric field changed from -0.03 a.u. to 0.05 a. u.,the bond length of O-H is increased. However,as the electric field changed from -0.06 a.u. to -0.03 a.u.,the bond length of O-H is decreased,because of the charge transfer induce by the applied electric field. But the bond angle of H2O are decreased as the electric field changed from -0.06 a.u. to 0.05 a. u. The dipole moment of the ground state decreases with the applied field strength. As the electric field increasing,the total energy of the molecule decreases. The excitation energies of the first six excited states of water molecule decrease as the increase of the applied electric field,indicating that the molecule is easy to be excited under electric field and hence it can be easily dissociated.