The Nonadiabatic Dynamic Research Of Photochemistry For 1,3-cyclohexadiene And Its Derivatives

This thesis has two main parts. In first part, we briefly describe the new Zhu-Nakamura algorithm incorporating with on-the-fly TSH approach which is developed by our group industriously, as well as the methods which can compute the energy and its analytic gradient in the process of dynamic simulation. In second part, we mainly introduced the photo-induced 1,3-cyclohexadiene(CHD) and M-diarylethene ring opening reaction dynamics simulation.The first chapter we briefly describe photochromic compound, including its definition, rough classification and wide application prospects firstly, then elaborated the sudy background of 1,3-cyclohexadiene and M-diarylethene, the last but not least we briefly introduced the new Zhu-Nakamura algorithm incorporating with on-the-fly TSH approach as well as the methods which can compute the energy and its analytic gradient in the process of dynamic simulation, including the complete-active-space self-consistent field (CASSCF) method and the internally contracted multi-reference configuration interaction (ICMRCI) method.In the second chapter we mainly discussed a newly developed algorithm, we could able to perform on-the-fly trajectory surface hopping molecular dynamics at the SA3-CASSCF(14, 8)/6-31G* quantum level to investigate the photo-induced 1,3-cyclohexadiene ring opening reaction from 1,3-cyclohexadiene (CHD) to 1,3,5-hexatriene (HT). We found four conical intersection zones within three singlet low-lying electronic states, in which 1B/2A and 1 A/2 A are well known to be the most important conical intersection zones to govern dynamics of ring opening reaction. The present simulation gained insight into nonadiabatic dynamics in which 516 sampling trajectories out of 600 can switch back and forth between two involved potential energy surfaces not only at 1B/2A, but also at 1A/2A. This insight is the key to influence quantum yields and time scales of the ring opening reaction. We estimated time constants as 46 fs,82 fs, and 120 fs, respectively for crossing 1B/2A and 1A/2A, and excited-state lifetime in comparison with corresponding experimental values 56 fs,80 fs and 130 fs. We estimated quantum yield 0.47/0.53 to HT/CHD in comparison to experiment values 0.30/0.70 in the gas-phase and 0.41/0.59 in the condense-phase. Moreover, the present simulation within 600 sampling trajectories indicates that there is no five membered ring forming.In the third chapter we present the photo induced M-DAE ring opening reaction dynamics simulation the study style which is as same as the second chapter about the CHD? HT reaction. The present run 200 trajectories in total in which the number of unreactive trajectories is 24 and the number of reactive trajectories is 176. The simulation estimated quantum yield about the opening product is 67.6% and the closing product is 32.4%, as well as the excited state lifetime is 70.8 fs. However, the result has some disagreements with the previous theory result, so we will do more research in the future.