利用涨落理论确定液体均匀核化速率

基于统计热力学涨落理论 ,按照能量涨落的概率分布规律提出了全新的计算过热液体均匀核化速率的理论 ,即系综中发生气化的系统数目取决于系综中能量涨落值达到形成稳定泡核的功量的概率 .针对吉布斯正则和巨正则系综推导了相应的计算公式 .新方法考虑了升温或降压速率对核化速率的影响 ,体现了均匀核化过程的动态特性 ,同时也表明均匀核化速率不是一种物性参数 .用所得公式对一些物质的均匀核化速率进行了计算 ,计算结果表明 ,涨落方法中核化速率随过热程度的变化较动力学方法计算结果平缓 ,在过热程度低时前者高于后者 ,在过热程度高时则相反 .同实验数据的对比证实了本文所提出的理论和公式的合理性

Prediction of the Homogeneous Nucleation Rate by Fluctuation Theory

A new hypothesis for predicting homogeneous nucleation rate in superheated liquids was proposed according to the probability distribution of energy fluctuation in statistical thermodynamic fluctuation theory. The number of systems that nucleation takes place in an ensemble was supposed to be decided by the probability that the energy fluctuation in the ensemble achieve the work needed to form a stable nucleus. Formulae for calculating the homogeneous nucleation rate in Gibbs canonical and grand canonical ensembles were deduced. The new method takes the temperature increase or pressure decrease speed into account, reflecting that the homogeneous nucleation process is dynamic, and the nucleation rate is not a physical property of materials. Sample calculating results of the nucleation rate of some substances by the new method and by the commonly used kinetic method were given. The former gives out a slower increase of nucleation rate when temperature rises or pressure drops than the latter. Contrasting between these results and experimental results was also given. It turns out that the new hypothesis as well as the new formulae is reasonable and applicable.