团簇异构体生长概率的理论预测

Theoretical prediction of the growth probabilities for cluster isomers

由于实验表征团簇结构的困难,理论预测团簇在生长过程中各种异构体的生成概率便十分重要.考虑到分子动力学可模拟高温时各异构体的相对丰度,把问题归结为高温时所形成的各种异构体在室温环境中如何转化,并建立了统计力学模型,得到了异构体相互演化所需时间与环境温度的解析关系.以C12团簇为例,在2500K时所形成的最可几异构体在室温环境中需要超过1012年才能转化为最低势能异构体.

Theoretically predicting probabilities of the various isomers in the cluster growth is important because of the difficulty in characterizing structure of clusters. Considering that relative abundance of each isomer formed at high temperature could be obtained through molecular dynamics,what the problem comes down to is how these isomers transform from one to another at room temperature. We developed a statistical mechanics model,and obtained the analytic relationship between the temperature and the transformation time from one isomer to another. Taking cluster C12 as an example,it is shown that the time for the most probable isomer formed at 2500 K turning into the isomer with the lowest potential energy at room temperature is longer than.