The Construction Potential Energy Surface And Dynamics Study Of ArH₂⁺System

The potential energy surface is an important concept in simulatingatom-molecule collision process. Ar+H2+reaction which has been typical and verysimple ion-molecule reactions is considered to be the prototype systems to test thequality of the new theories and experiments. As is known, every dynamicssimulation is based on the potential energy surface. And our group constructed an abinitio PES (LLZ PES) for the ground state of the Ar+H2+â†'ArH++H reaction usingthe coupled-cluster theory including all single and double excitations plusperturbative corrections for the triples UCCSD(T) with a large orbital basis set ofaug-cc-pV5Z. Although the method is very accurate around the equilibrium bonddistance, it breaks down at larger distances of two atoms, which means thecalculation fails to converge and further negatively affects the precision of the PES.Therefore, we present a new more accurate potential energy surface for ground stateof the title reaction using multi-reference configuration interaction method (MRCI)with Davidson correction and a basis set of aug-cc-pVQZ.This dissertation is composed of two main parts. The first part tells how toconstructs the Ar+H2+system potential energy surface of the ground state. And thesecond part shows that we studied the kinetic property of the reaction ofAr+H2+â†'ArH++H using the time-dependent wave packet method and thequasi-classical trajectory method in order to detect the potential energy surface.In this paper, the chapter content is as follows. In the first chapter we made asimple introduction of molecular reaction dynamics which contains the developmentsof molecular reaction dynamics and the basic conception potential energy surface aswell as how to get the energy of single point. The second chapter shows the time-dependent wave packet theory and the vector correlation and related theories ofQCT. The third and the fourth chapter shows the main work of this paper. We tell theprocedures of how to conduct the three-dimensional potential energy surface ofAr+H2+system in detail in the third chapter. In the fourth chapter, we have alsocarried out a three-dimensional time-dependent wave-packet scattering calculationsfor the Ar+H2+(vi=0, ji=0)â†'ArH++H reaction over the collision energy range0.03-1.0eV by employing our new PES. We have compared the present theoreticalCC and CS cross sections with the results of experiment, and found that the calculatedCC cross section is in agreement with the experimental measurement at collisionenergy1.0eV. Moreover, through the comparison of the differences between the CCand CS cross sections, we find that the value of CS approximation is slightly less thanthat of CC at collision energy ET>0.3eV, which indicates that the CC effects arepronounced in the title reaction, and the calculations of the reactionAr+H2+â†'ArH++H using quasi-classical trajectory results show that the integralreaction cross section are well consistent with the experimental values at differentcollision energies and reagent’s vibrational excitations, which indicates that ourpotential energy surface is accurate. The results indicate that the vibration excitationhas less impact on theP (θ r)distributions than the collision energy does. TheP (φ r)distributions, the PDDCSs are quite sensitive to different collision energy andreagent’s vibrational excitation.