质子与羟基碰撞的含时密度泛函理论研究

采用将含时密度泛函理论和分子动力学非绝热耦合的方法,研究了不同入射速度下质子与羟基碰撞的反应动力学.计算了碰撞前后质子动能和羟基动能的变化及羟基电子和质子的运动.计算结果表明,质子沿垂直羟基分子轴方向入射时,质子与羟基碰撞后,质子被反弹且动能损失并俘获了羟基中氧的一部分电子,而丢失部分电子的羟基则获得动能以伸缩振动的形式向计算边界平动.随着入射质子的初动能增加,质子从羟基中俘获的电子增多,碰撞后羟基的键长变长,羟基振动变强而伸缩振动频率降低.此外,还发现质子的入射方向对碰撞过程的激发动力学有很大的影响.质子从不同的方向入射时,质子的入射初动能越大,其损失的动能越多且损失的动能与入射初动能呈线性关系,而入射方向对质子动能损失的影响很小.在质子入射初动能较低(小于25 eV)的情况下,羟基获得的动能与质子入射初动能呈线性关系且与入射方向无关;在质子入射初动能较高(大于25 eV)时,当质子沿羟基分子轴方向入射时,羟基动能的增量远大于质子沿垂直于羟基分子轴方向入射时羟基动能的增量.

Time-dependent density functional theory studies of dynamics of hydroxy by proton impact

Using the time-dependent density functional theory and non-adiabatic coupling in molecular dynamics, the reaction dynamics of collisions between energetic proton and hydroxy is studied. The variations in kinetic energy of proton and hydroxy and the motions of electron of hydroxyl and ion before and after collisions are investigated. It is found that when a proton is incident in the direction perpendicular to the molecular axis, it that has lose kinetic energy rebounds, and captures electrons from hydroxy, while the hydroxy that has lost part of electrons gains kinetic energy, and thus translates toward the calculating boundary in the manner of contracting vibration. The larger the kinetic energy of incident proton, the more the number of electrons captured from hydroxy is. Therefore the bond length of hydroxy lengthens, oscillation strengthens, and vibrational frequency decreases. In addition, it is found that the incident direction of proton has a great influence on the dynamic behavior of excitation in a collision process. Considering the case where the proton is incident from different directions, the results show that the larger the kinetic energy of incident proton, the more the lost energy is, and the lost energy is linearly related to the initial kinetic energy of incident proton. For hydroxy, when the incident kinetic energy of proton is less than 25 eV, the kinetic energy gained by the proton is linearly related to the initial kinetic energy, but unrelated to incident direction, while when the initial kinetic energy of incident proton is larger than 25 eV, the increment in kinetic energy of hydroxyl is much larger in the case where the proton is incident along the axis of hydroxyl molecule than in the case where the proton is incident in the direction perpendicular to the axis of the hydroxyl molecule.