On the basis of ab initio Gibbs ensemble Monte Carlo simulations, we map the liquid–vapor phase diagram of water described by the RPBE density functional supplemented by D3 dispersion corrections and estimate the critical point by density extrapolation. Knowing the approximate location of the critical point, two sets of ab initio molecular dynamics simulations at gas-like and liquid-like densities deep in the supercritical phase of water are carried out where particular attention is payed to ergodic sampling in view of large correlation lengths and long correlation times. Structural, H-bonding, and dipolar properties of RPBE-D3 water are analyzed along the liquid–vapor coexistence curve upon moving toward the critical point and compared to those in the supercritical state. The properties of high-density supercritical water are astonishingly similar to those of the liquid on the coexistence curve under subcritical conditions at comparable density. Upon decomposing the molecular dipole moments into purely configurational and electronic polarization/charge-transfer contributions, it is demonstrated that the latter play a decreasing role in liquid water upon approaching the critical point on the coexistence curve. Moreover, these many-body effects are systematically suppressed in supercritical water due to the significantly reduced H-bonding network.

中文翻译：

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RPBE-D3水的液相-液相图：沿着共存曲线和超临界相的电子性质

在从头算Gibbs系谱蒙特卡洛模拟的基础上，我们绘制了由RPBE密度函数描述的水的液相-气相图，并通过D3色散校正进行了补充，并通过密度外推法估算了临界点。知道临界点的大致位置，在水的超临界相中深处的气体样和液体样密度下进行了两组从头算分子动力学模拟，其中鉴于大的相关长度，特别要注意遍历取样和较长的相关时间。RPBE-D3水的结构，氢键和偶极性质在到达临界点时沿着液-汽共存曲线进行分析，并与超临界状态下的水进行比较。高密度超临界水的性质与亚临界条件下可比密度下的共存曲线上的液体性质惊人地相似。将分子偶极矩分解为纯构型和电子极化/电荷转移贡献后，证明了当接近共存曲线上的临界点时，后者在液态水中的作用逐渐减弱。此外，由于显着减少的氢键网络，在超临界水中系统地抑制了这些多体效应。结果表明，当接近共存曲线上的临界点时，后者在液态水中的作用逐渐减弱。此外，由于显着减少的氢键网络，在超临界水中系统地抑制了这些多体效应。结果表明，当接近共存曲线上的临界点时，后者在液态水中的作用逐渐减弱。此外，由于显着减少的氢键网络，在超临界水中系统地抑制了这些多体效应。