中文摘要：

高温高压下流体氢将发生离解化学反应,形成具有相互作用的氢分子和氢原子混合体系,此时粒子间的相互作用复杂.利用单组分流体近似的范德瓦尔斯混合模型,将混合物粒子间的相互作用等效为单组分粒子间相互作用,从而简化了对体系的统计热力学处理;并由自由能函数极小化确定化学平衡时各组分含量、体系的内能、压强.研究了温度在10 000 K以下、密度在0.6 g/cm^3以下（相应摩尔体积大于3.3 cm^3/mol）区间的热致离解和压致离解现象对流体氢（氘）状态方程的影响.所得结果与双组分流体变分理论计算以及第一原理的分子动力学模拟、蒙特卡罗模拟结果以及二级轻气炮实验数据进行了比较,它们之间的一致性表明：用单组分流体近似的范德瓦尔斯混合模型处理氢（氘）分子的离解区域的物态方程是成功的.

英文摘要：

Molecular hydrogen and deuterium under high temperature and high density conditions may undergo dissociation reaction, and thus transforms to an interacting mixture composed of molecules and atoms with complex interactions between constituent particles. In this paper, we use one-component fluid van der Waals （VDWLF） mixture approximation,in which an equivalent one-component potential is utilized to describe that compression behavior of such a mixture system in order to simplify the statistical thermodynamic treatment, and, therefore, calculate the internal energy and pressure of this system and concentration for each constituents through Helmholtz free energy minimization. The dissociation effects including temperature- and pressure-induced are studied in the density and temperature range of p≤0. 6 g/cm^3 （corresponding molar volume V≥3. 3 cm^3/mol） and T≤10000K,respectively. The calculated isothermal equations of state of hydrogen are basically in agreement with those calculated by the two-component fluid variational theory and the first principle molecular dynamics and Monte Carlo simulations. The calculated single shock and double shock Hugoniots for molecular deuterium are also in well accord with experiments. The above mentioned results demonstrate the VDWLF mixture approximation is valid for the compression behavior descriptions of hydrogen （deuterium） within the region of p≤0.6 g/cm^3（corresponding molar volume V≥3.3 cm^3/mol） and T≤10000 K.