Pruteanu Ciprian G, Naden Robinson Victor, Ansari Narjes, Hassanali Ali, Scandolo Sandro, Loveday John S
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
The "Abdus Salam" International Centre for Theoretical Physics, I-34151 Trieste, Italy.
J Phys Chem Lett. 2020 Jun 18;11(12):4826-4833. doi: 10.1021/acs.jpclett.0c01410. Epub 2020 Jun 8.
The molecular structure of dense homogeneous fluid water-methane mixtures has been determined for the first time using high-pressure neutron-scattering techniques at 1.7 and 2.2 GPa. A mixed state with a fully H-bonded water network is revealed. The hydration shell of the methane molecules is, however, revealed to be pressure-dependent with an increase in the water coordination between 1.7 and 2.2 GPa. In parallel, molecular dynamics simulations have been performed to provide insight into the microscopic mechanisms associated with the phenomenon of mixing. These calculations reproduce the observed phase change from phase separation to mixing with increasing pressure. The calculations also reproduce the experimentally observed structural properties. Unexpectedly, the simulations show mixing is accompanied by a subtle enhancement of the polarization of methane. Our results highlight the key role played by fine electronic effects on miscibility and the need to readjust our fundamental understanding of hydrophobicity to account for these.
首次利用高压中子散射技术在1.7吉帕和2.2吉帕压力下测定了致密均匀的水 - 甲烷混合流体的分子结构。揭示了一种具有完全氢键连接水网络的混合状态。然而，甲烷分子的水化层显示出与压力相关，在1.7吉帕至2.2吉帕之间水配位增加。同时，进行了分子动力学模拟，以深入了解与混合现象相关的微观机制。这些计算再现了随着压力增加从相分离到混合的观察到的相变。计算还再现了实验观察到的结构性质。出乎意料的是，模拟显示混合伴随着甲烷极化的微妙增强。我们的结果突出了精细电子效应在混溶性中所起的关键作用，以及重新调整我们对疏水性的基本理解以考虑这些效应的必要性。
