外电场作用下MgO分子的特性研究

Study on structure characteristics of MgO molecule under external electric field

采用密度泛函理论的B3LYP方法在6-311+G(2DF)水平上研究了电场强度为-0.03—0.03a.u.的外电场对MgO基态分子的几何结构、HOMO能级、LUMO能级、能隙、费米能级、谐振频率和红外光谱强度的影响规律.结果表明,在所加的电场范围内,随着正向电场的增大核间距先减小后增大,在F=0.02a.u.时,Re取得最小为0.17397nm;分子总能量不断升高,但增大的幅度呈减小的趋势;EH先增大后减小,在F=0.01a.u.处取得最大,其值为-0.21765a.u;而EL和Eg则始终减小.随着正向电场的逐渐增大,振动频率逐渐减小.外电场对MgO分子的激发能、振子强度及红外振动光谱的位置和强度均有较大影响.

The influence of external electric field ranging from - 0.03 to 0.03 a.u. on the equilibrium geometry, HOMO energy level, LUMO energy level, energy gap, harmonic frequency and infrared intensity of MgO ground state molecule is investigated by employing the density functional methods （B3LYP） with basis sets 6-311 ＋ G（2DF）. The results show that the LUMO energy level, energy gap and harmonic frequency decrease, but the total energy increases with increasing external field. The bond length is proved firstly decreasing, then increasing, however, the HOMO energy level is proved firstly increasing, then decreasing with increasing external field. The maximum of HOMO energy level and minimum of bond length are - 0.21765 a.u. at F = 0.01 a.u. and 0. 17397 nm at F = 0.02 a. u, respectively. The external electric field has effect on excitation energies, oscillator strengths and the position and intensity of infrared spectrum.