早期太阳星云原子团簇统计热力学的定态模型

THE STATISTICAL THERMODYNAMICS STEADY MODEL ABOUT THE ATOMIC CLUSTERS IN PRIMITIVE SOLAR NEBULA

从Fe：Mg：Si：O＝1：1：1：4的早期太阳星云中原子的两体碰撞频率开始，对均匀稳恒状态下某一特定团簇的碰撞几率和有效碰撞数的表达式进行了讨论，并建立了一个稳恒状态下的统计热力学定态模型。然后利用这一模型和模拟实验的结果计算了太阳星云中几种主要原子团簇相对内能的大小以及不同平衡态下的分布。

Starting from the two-body co11lsion frequency of the atoms in primitive solar nebula where the Fe: Mg: Si: O is 1: 1: 1: 4, this paper discussed and calculated the probability of collislon and the formula of effective collision number. The collision probability of a certain cluster (pk) which consists of K atoms can be got from the following formula: The statistical thermodynamlcs steady model has be given as the formula (2):The interrelated diagram between the frequency (logNk) and the density (logn) on the state of T= 104K has also been calculated as Fig.1. From this figure, we can see that Nk in creases with the growth of n, and the growth range increases with the increment of K. Besides, when n is less than 1018cm-3, the collision frequency of small K cluster is larger than that of big K cluster, but when n is larger than 1020cm-3, it is just the opposite. When n is near 1019 cm-3, the collision frequency (Nk) values of the atomic clusters with different K values are nearly the same.Given an average temperature (T) and a nebula density (n), we can calculate the dlstribution of a certain cluster with a fixed internal energy (Uk) value by formula (2).The U. values listed in Table 2 are calculated depending on formula (2) where the nK values of different clusters are taken from the simulation experiments of CV3 chondrite (see Table 1).The. U. values listed in Table 2 may be somewhat too large, because there are some approximation in the calculation process of steady model. The more preclse calculation is still on the way. It will depend on the establishment of statistical thermodynamics model in an unbalanced state.