Theoretical Studies Of Dynamics Properties Of The LiH₂System

LiH₂system plays an important role in the progress of the origin of univers and thecomic evolution in the early universe,there are many increasing interests in the experimentaland theoretical study.Although LiH₂system includes few electronics,it has so many basiccharacteristics like other complex systems.so our study of this system will lay a solidfoundation on other complex systems.As a typical molecule reaction, LiH+H system lack ofkinetic information for many progress,especially for the corresponding stereodynamicsinformation.In this paper,in the basis of the new PES given by P,etc in2009,we have thetheoretical study and calculation on the dynamics characteristics and the isotope effect usingthe QCT theory.1. Employing the ground state PESs which constructed by P et al, we calculated thedynamics characteristics of the H+LiH（v=0,12,3）→H2+Li reaction using QCTmethod.Firstly,we calculated the reaction probabilities and integral reaction cross sections ofthe reactant in three different vibrations,through the observation, we know that the integralreaction cross sections is reduced with the increasing vibration numbers and collisionenergy,it is can be proved that the PES which constructed by P et al is reallybarrier-less.Then,we observed four PDDCSs in0.05eV，0.5eV，0.8eV,2.6eV collision and inthree vibration quantum state,it illusted that the reaction is mainly dominated by the directreaction mechanism.In addition,we calculated the vector-related,such as P （θ r）、 P （φ r）and<P2（j′k）>,we obtained that whether the reactant directed to the positive or negative ofY-axis is mainly deterimented by the low or high of the collision energy,but there is littleeffects on the orientation.Finally,we calculated the reaction trajectory of the reaction H+LiHto discuss if there are intermediate product and its condition to occur.2. Based on the new PES constructed by P et al,we studied the isotope reaction of LiH₂system.we use QCT method calculated the reaction probabilities and integral reaction crosssections of the reaction H+LiH/D（v=0,j=0）→H2/HD+Li and compared the two reactions.Aswe know,the isotope effect has less effect on the integral reaction cross sections, thereaction probabilities is increased when the collision energy is less than0.25eV and inducedwhen the collision energy is more than0.25eV. Then we calculated the four PDDCSs andtheir vector-related,respectively in low and high collision energy.It can be seen from the figure that the reaction is mainly forward scattering,and the scattering degree is increasedwith the increasing collision energy,its product rotational angular momentum j’（in a verysmall scattering angle range） tend to be distributed in the vertical direction of K,in addition,itis obviously effected by the low and high collision energy. It can be said that the mass of thetarget molecule plays less important role in the stereodynamics.The PES which constructed by P et al is more accurate than the others.The experience inthe establishment of analytical potential energy of the tratomic molecules laid a soildfoundation for us to study the ground state of analytical potential energy surface of LiH₂system.As the LiH₂system has a high hydrogen percentage,the study above will also help usfind a high-performance hydrogen storage materials.