Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
J Chem Phys. 2012 Nov 28;137(20):204505. doi: 10.1063/1.4767898.
Ice Ih is arguably the most important molecular crystal in nature, yet our understanding of its structural and dynamical properties is still far from complete. We present embedded-fragment calculations of the structures and vibrational spectra of the three-dimensional, proton-disordered phase of ice Ih performed at the level of second-order many-body perturbation theory with a basis-set superposition error correction. Our calculations address previous controversies such as the one related to the O-H bond length as well as the existence of two types of hydrogen bonds with strengths differing by a factor of two. For the latter, our calculations suggest that the observed spectral features arise from the directionality or the anisotropy of collective hydrogen-bond stretching vibrations rather than the previously suggested vastly different force constants. We also report a capability to efficiently compute infrared and Raman intensities of a periodic solid. Our approach reproduces the infrared and Raman spectra, the variation of inelastic neutron scattering spectra with deuterium concentration, and the anomaly of heat capacities at low temperatures for ice Ih.
冰 Ih 可以说是自然界中最重要的分子晶体，但我们对其结构和动力学性质的理解仍远远不够。我们在二阶多体微扰理论水平上进行了嵌入片段计算，对冰 Ih 的三维质子无序相的结构和振动光谱进行了计算，并进行了基集叠加误差校正。我们的计算解决了以前的争议，例如与 O-H 键长有关的争议，以及存在两种强度相差两倍的氢键的争议。对于后者，我们的计算表明，观察到的光谱特征来自氢键伸缩振动的方向性或各向异性，而不是以前提出的力常数大不相同。我们还报告了一种有效计算周期性固体红外和拉曼强度的能力。我们的方法再现了冰 Ih 的红外和拉曼光谱、与氘浓度变化相关的非弹性中子散射光谱以及低温下热容的异常。
