Stubbs John M, Siepmann J Ilja
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA.
J Chem Phys. 2004 Jul 15;121(3):1525-34. doi: 10.1063/1.1763842.
Configurational-bias Monte Carlo simulations in the Gibbs and isobaric-isothermal ensembles using the transferable potentials for phase equilibria force field were carried out to investigate the thermophysical properties of mixtures containing supercritical carbon dioxide and methanol. The binary vapor-liquid coexistence curves were calculated at 333.15 and 353.15 K and are in excellent agreement with experimental measurements. The self-association of methanol in supercritical carbon dioxide was investigated over a range of temperatures and pressures near the mixture critical point. The temperature dependence of the equilibrium constants for the formation of hydrogen-bonded aggregates (from dimer to heptamer) allowed for the determination of the enthalpy of hydrogen bonding, DeltaHHB, in supercritical carbon dioxide with values for DeltaHHB of about 15 kJ mol(-1) falling within the range of previously proposed values. No strong pressure dependence was observed for the formation of aggregates. Apparently the decrease of the entropic penalty and of the enthalpic benefit upon increasing pressure or solvent density mostly cancel each other's effect on aggregate formation.
利用相平衡力场的可转移势能，在吉布斯系综和等压等温系综中进行了构型偏置蒙特卡罗模拟，以研究含有超临界二氧化碳和甲醇的混合物的热物理性质。计算了333.15 K和353.15 K下的二元气液共存曲线，与实验测量结果吻合良好。研究了在混合物临界点附近的一系列温度和压力下，甲醇在超临界二氧化碳中的自缔合。形成氢键聚集体（从二聚体到七聚体）的平衡常数的温度依赖性使得能够确定超临界二氧化碳中氢键的焓变ΔHHB，其ΔHHB值约为15 kJ mol(-1)，落在先前提出的值范围内。未观察到聚集体形成对压力有强烈依赖性。显然，随着压力或溶剂密度增加，熵罚和焓利的降低对聚集体形成的影响大多相互抵消。
