超临界氮的四参数立方型状态方程与分子动力学模拟  

Four-parameter cubic equation of state and molecular dynamics simulation of supercritical nitrogen

作　　者：姜思雨 郭涛 胡家文 JIANG Siyu;GUO Tao;HU Jiawen(Hebei Key Laboratory of Strategic Critical Mineral Resources,Hebei GEO University,Shijiazhuang 050031,Hebei,China;College of Earth Science,Hebei GEO University,Shijiazhuang 050031,Hebei,China;School of Mathematics and Science,Hebei GEO University,Shijiazhuang 050031,Hebei,China)

机构地区：[1]河北地质大学河北省战略性关键矿产资源研究重点实验室,河北石家庄050031 [2]河北地质大学地球科学学院,河北石家庄050031 [3]河北地质大学数理教学部,河北石家庄050031

出　　处：《地球化学》2022年第3期344-364,共21页Geochimica

基　　金：河北省自然科学基金(D2018403089);河北省高等学校科学技术研究重点项目(ZD2018026);河北省研究生创新资助项目(CXZZSS2020112)联合资助。

摘　　要：根据精确的压力–摩尔体积–温度(PVT)数据及其外延结果,本研究建立了超临界氮(N2)的四参数立方型状态方程。新方程最适宜的条件为273~4273 K、0~0.85 g·cm^(-3)。在此范围内,新方程的最大体积偏差在0.41%以内,平均体积偏差在0.1%以内;等温线的压力范围随着温度的上升而扩大,最大压力达2.9GPa。当密度增至1.03 g·cm^(-3)、温度增至5000 K时,体积偏差在0.6%~2.50%以内,最高压力达3.3~5.0 GPa。新方程也可近似地应用到密度为1.2 g·cm^(-3)。此时相应的温压可达5573 K、7.5 GPa。此外,本研究还用分子动力学方法模拟了超临界氮在1473~5073 K、0.3~6.0 GPa范围内的PVT性质。所得结果以及现有的高温或高密度实验数据、分子动力学和蒙特卡洛(Monte Carlo)模拟数据(0.1~1.2 g·cm^(-3))均与新方程吻合得很好或较好。由新方程预测的逸度系数、剩余焓、剩余熵及其他热力学性质与参考模型的计算值均很吻合。这些结果表明新方程显著地优于现有的立方型、维里型和更复杂的地质流体状态方程。A four-parameter cubic equation of state for supercritical nitrogen(N2) was developed using highly accurate pressure-volume-temperature(PVT) data and their extrapolation results. The conditions that best fit the new equation are 273–4273 K and 0–0.85 g·cm^(-3). In this range, the average and maximum volume deviations of the new equation are less than 0.1% and 0.41%, respectively;the range of pressure of an isotherm increases with increasing temperature, so the maximum pressure may rise to 2.9 GPa. When density increases to 1.03 g·cm^(-3)and temperature increases to 5000 K, the volume deviations are within 0.6%–2.5%, and the maximum pressure increases to 3.3–5.0 GPa. The new equation can also be approximately used up to 1.2 g·cm^(-3), below which the maximum temperature and pressure reach 5573 K and 7.5 GPa, respectively. In addition, the PVT properties of N2at 1473–5073 K and 0.3–6.0 GPa were simulated using molecular dynamics. These results, along with the existing experimental data and molecular dynamics or Monte Carlo simulation results at high temperatures or densities(0.1–1.2 g·cm^(-3)), are in good or excellent agreement with the new equation. The fugacity coefficient, residual enthalpies, residual entropies, and other thermodynamic properties predicted by the new equation agree very well with those calculated by the reference model. These results indicate that the new equation is significantly better than existing cubic, virial-type, and more complex equations of state for geofluids.

关 键 词：超临界氮 状态方程 PVT性质 逸度系数 剩余焓 分子动力学 

分 类 号：O41[理学—理论物理] O642[理学—物理]