Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study and Institute of Mathematical and Natural Sciences, Massey University Albany , Private Bag 102904, Auckland 0745, New Zealand.
J Phys Chem B. 2014 Mar 27;118(12):3392-400. doi: 10.1021/jp412260a. Epub 2014 Mar 19.
We report a sixth-order ab initio virial equation of state (EOS) for mercury. The virial coefficients were determined in the temperature range from 500 to 7750 K using a three-body approximation to the N-body interaction potential. The underlying two-body and three-body potentials were fitted to highly accurate Coupled-Cluster interaction energies of Hg2 (Pahl, E.; Figgen, D.; Thierfelder, C.; Peterson, K. A.; Calvo, F.; Schwerdtfeger, P. J. Chem. Phys. 2010, 132, 114301-1) and equilateral-triangular configurations of Hg3. We find the virial coefficients of order four and higher to be negative and to have large absolute values over the entire temperature range considered. The validity of our three-body, sixth-order EOS seems to be limited to small densities of about 1.5 g cm(-3) and somewhat higher densities at higher temperatures. Termwise analysis and comparison to experimental gas-phase data suggest a small convergence radius of the virial EOS itself as well as a failure of the three-body interaction model (i.e., poor convergence of the many-body expansion for mercury). We conjecture that the nth-order term of the virial EOS is to be evaluated from the full n-body interaction potential for a quantitative picture. Consequently, an ab initio three-body virial equation cannot describe the mercury gas phase.
我们报道了汞的第六阶从头算维里状态方程（EOS）。维里系数是在 500 到 7750 K 的温度范围内使用 N 体相互作用势的三体近似确定的。基础的两体和三体势拟合了高度精确的 Hg2 的耦合簇相互作用能（Pahl，E.；Figgen，D.；Thierfelder，C.；Peterson，K. A.；Calvo，F.；Schwerdtfeger，P. J. Chem. Phys. 2010，132，114301-1）和等边三角形 Hg3 配置。我们发现四阶和更高阶的维里系数为负，并且在整个考虑的温度范围内具有较大的绝对值。我们的三体六阶 EOS 的有效性似乎仅限于大约 1.5 g cm(-3)的小密度和更高温度下的稍高密度。逐项分析和与实验气相数据的比较表明维里 EOS 本身的收敛半径较小，以及三体相互作用模型的失败（即汞的多体展开的收敛较差）。我们推测维里 EOS 的第 n 阶项应根据完整的 n 体相互作用势来评估，以获得定量图像。因此，从头算三体维里方程不能描述汞气相。
