Origin of Anomalous Thermal Expansion in Ih phase of Protonated (H2O) and Deuterated (D2O) ice

Among the all known crystalline ice phases, ice (Ih phase) exhibits anomalous thermal expansion behavior. We propose to measure phonon density of state of protonated ice (H2O) and deuterated ice (D2O) in Ih phase at 240 K at different pressures up to 1.8 kbar. The measurements will enable to determination of the energy dependence of the Grüneisen parameters strictly in Ih phase thereby quantitative calculation of the thermal expansion coefficient from phonon data to be undertaken. Apart from the pressure studies, we would also like to measure the temperature dependence of phonon frequencies in the Ih phase of both the protonated (H2O) and deuterated ice (D2O). The combination of temperature and pressure measurements would help to determine the implicit as well as explicit anharmonicities. We also plan to do ab-initio calculations for analysis of the experimental data.在所有已知的结晶冰相中，冰（Ih相）展现出反常的热膨胀行为。我们拟对240 K、最高压力达1.8 kbar的Ih相质子化冰（H₂O）与氘化冰（D₂O）的声子态密度（phonon density of state）开展测量。该测量可严格针对Ih相确定格林艾森参数（Grüneisen parameters）的能量依赖性，进而可基于声子数据完成热膨胀系数的定量计算。除压力相关研究外，我们还将测定质子化冰（H₂O）与氘化冰（D₂O）的Ih相中声子频率的温度依赖性。结合温度与压力的测量结果，将有助于解析隐式与显式非简谐性。我们还计划开展从头算（ab-initio calculations）以分析实验数据。