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理论计算稳定同位素平衡分馏因子(α),是以计算平衡常数K为桥梁,但是K与α之间并非简单的指数关系,二者之间还存在一个较为神秘的过量因子X(excess factor)。然而,几乎所有的理论计算工作都直接忽略了过量因子,并没有人详细研究过过量因子的实质及其可以被忽略的条件,因此,针对这个现状,本文从最基础的理论推导开始,精确推导了α和K之间的关系,并得到了过量因子的具体表达式,同时也给出了β因子(一种物质与其理想气态原子之间的平衡分馏因子)和同位素约化配分函数比(RPFR)之间的具体关系式。本文还以石膏与溶液中硫酸根之间的硫和氧同位素的分馏为实例,具体展示了过量因子产生的原因和计算方法,也提供了精确的石膏和硫酸根之间的硫和氧同位素的平衡分馏参数。
Theoretical calculation of stable isotope equilibrium fractionation factor (α) is based on the calculation of the equilibrium constant K as a bridge, but not a simple exponential relationship between K and α, and a more mysterious excess factor X exists between the two. However, almost all the theoretical calculations directly ignore the excess factor, and no one has studied in detail the essence of the excess factor and its conditions that can be ignored. Therefore, in light of this status quo, this article starts from the most basic theoretical derivation and deduces precisely The relationship between α and K is obtained and the specific expression of the excess factor is obtained. The β factor (the equilibrium fractionation factor between a substance and its ideal gaseous atom) and the isotope reduction ratio (RPFR ) The specific relationship between. In this paper, we also take the fractionation of sulfur and oxygen isotopes between sulfate and gypsum in gypsum as an example to show the reasons and calculation methods of excess factors, and also provide accurate sulfur and oxygen isotopes between gypsum and sulfate Balance fractionation parameters.