Clathrate hydrates are ubiquitous in terrestrial oceans or asteroids in the solar system, attracting the attention of scientists and forming an unstoppable research wave. Here, we study 9 ice phases of the empty clathrate hydrates sII, sIII, sIV, sH, dtc, EMT, sL, ITT and ice XI at negative pressures based on the second-order Møller-Plesset perturbation (MP2) theory and the higher-level CCSD(T) theory. A renewed phase diagram at negative pressures is proposed, where the empty hydrates sII, dtc, and EMT are demonstrated to be thermodynamical stable from −0.26 to −0.80 GPa. The predicted lattice parameters and Raman spectra of empty clathrate ices are in excellent agreement with the observable results, which validates the accuracy of the proposed methods in predicting the structures and phase diagram. The proposed work is crucial to the exploration of ice polymorphs and the scientific understanding of the properties of molecular crystals at negative pressures.

笼形水合物在陆地海洋或太阳系中的小行星中无处不在，引起了科学家的注意，并形成了不可阻挡的研究浪潮。在这里，我们基于二阶Møller-Plesset摄动（MP2）理论和更高的理论，研究了空包合物水合物sII，sIII，sIV，sH，dtc，EMT，sL，ITT和冰XI的9个冰相在负压下的情况。级CCSD（T）理论。提出了一个新的负压相图，其中空的水合物sII，dtc和EMT被证明在-0.26至-0.80 GPa范围内是热力学稳定的。空包冰的预测晶格参数和拉曼光谱与可观察到的结果非常吻合，这证明了所提方法在预测结构和相图方面的准确性。