Okuchi Takuo, Cody George D, Mao Ho-Kwang, Hemley Russell J
Geophysical Laboratory, Carnegie Institution of Washington, DC 20015, USA.
J Chem Phys. 2005 Jun 22;122(24):244509. doi: 10.1063/1.1944732.
Liquid methanol at densities up to rhorho(0) = 1.7 was studied by NMR in a specially designed diamond-anvil cell. Methyl and hydroxyl resonances have been separately observed at pressures to 43 kbars which exceeds equilibrium freezing pressure of methanol. The chemical shift difference between methyl and hydroxyl protons increases nonlinearly with increasing density, indicating a noticeable decrease in hydrogen bond length. The analyses of spin-lattice relaxation rates of both hydroxyl and methyl protons indicate that compression enhances intermolecular proton exchange and selectively reduces motion of the hydroxyl protons. Collectively these observations reveal that hydrogen bonding interaction in liquid methanol noticeably increases with compression, inhibiting the liquid-solid transition even above the freezing pressure.
在一个专门设计的金刚石对顶砧池中，通过核磁共振（NMR）研究了密度高达ρ(0)=1.7的液态甲醇。在高达43千巴的压力下分别观测到了甲基和羟基的共振信号，该压力超过了甲醇的平衡凝固压力。甲基和羟基质子之间的化学位移差异随密度增加而非线性增加，这表明氢键长度显著减小。对羟基质子和甲基质子的自旋晶格弛豫率的分析表明，压缩增强了分子间质子交换，并选择性地降低了羟基质子的运动。这些观测结果共同表明，液态甲醇中的氢键相互作用随压缩显著增加，即使在高于凝固压力的情况下也能抑制液-固转变。
