Titan大气中可能生成NH3的几个反应的量子力学计算

运用耦合簇理论CCSD方法和全组态CBS-Q理论对文献（Planet Space Sci，2003，51：1003-1011．）提出的Titan大气中可能生成NH3的6个链式反应进行了热化学计算和分析．发现：（a）反应（4）-（6）在Titan环境中反应能够正向进行，具有较大的自发反应趋势，反应（2）和（3）不具有反应自发性，在低温下自发反应可能性更低；（b）反应（2）的转变温度为955．14K，高于这个温度反应才有可能正向进行；（c）可以认为这6个链式反应在Titan大气的低温环境中自然合成NH3是不太可能的；（d）耦合簇理论CCSD方法和全组态CBS-Q理论的计算结果相吻合，互相印证了结论的可靠性．

A Quantum-mechanical Study on Possible Reactions Forming Ammonia in Titan's Atmosphere

In this paper,the thermodynamical properties of reactions(Planet Space Sci,2003,51:1003-1011.) have been calculated and discussed by means of coupled cluster single and double excitation(CCSD) theory at the CCSD/cc-pvdz and CBS-Q levels.The geometries of the reactants and products of reactions have been optimized,and the energies of the reactions and the equilibrium constant K of reactions have been computed.The analysis of the results shows as follows:(a) The free energies of reactions(4)-(6) are negative.It means that reactions could take place spontaneously in Titan's environment but reactions(2) and(3) could not take place spontaneously.(b) The converted temperature of reaction(2) is 955.14 K.(c) It is impossible for these six chain reactions to synthesize ammonia in Titan's atmosphere at lower temperatures.(d) The result of CCSD method is in agreement with that of CBS-Q theory.They verify the reliability for each other.We considered that this chain reaction might not be a pathway for the synthesis of ammonia in Titan's atmosphere.