Ab Initio Prediction of the Phase Transition for Solid Ammonia at High Pressures

Lei Huang; Yanqiang Han; Jinyun Liu; Xiao He; Jinjin Li

doi:10.1038/s41598-020-64030-3

Ab Initio Prediction of the Phase Transition for Solid Ammonia at High Pressures

Sci Rep. 2020 May 5;10(1):7546. doi: 10.1038/s41598-020-64030-3.

Authors

Lei Huang^{1

2}, Yanqiang Han¹, Jinyun Liu³, Xiao He^{4

5}, Jinjin Li^{6

7}

Affiliations

¹ Key laboratory for Thin Film and Microfabrication of the Ministry of Education, Department of Micro/Nano-electronics, Shanghai Jiao Tong University, Shanghai, 200240, China.
² Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China.
³ Key Laboratory of Functional Molecular Solids of the Ministry of Education, Anhui Laboratory of Molecule-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui, 241000, China. jyliu@ahnu.edu.cn.
⁴ Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China. xiaohe@phy.ecnu.edu.cn.
⁵ NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai, 200062, China. xiaohe@phy.ecnu.edu.cn.
⁶ Key laboratory for Thin Film and Microfabrication of the Ministry of Education, Department of Micro/Nano-electronics, Shanghai Jiao Tong University, Shanghai, 200240, China. lijinjin@sjtu.edu.cn.
⁷ Key Laboratory of Functional Molecular Solids of the Ministry of Education, Anhui Laboratory of Molecule-Based Materials, College of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui, 241000, China. lijinjin@sjtu.edu.cn.

Abstract

Ammonia is one of the most basic components on the planet and its high-pressure characteristics play an important role in planetary science. Solid ammonia crystals frequently adopt multiple distinct polymorphs exhibiting different properties. Predicting the crystal structure of these polymorphs and under what thermodynamic conditions these polymorphs are stable would be of great value to environmental industry and other fields. Theoretical calculations based on the classical force fields and density-functional theory (DFT) are versatile methods but lack of accurate description of weak intermolecular interactions for molecular crystals. In this study, we employ an ab initio computational study on the solid ammonia at high pressures, using the second-order Møller-Plesset perturbation (MP2) theory and the coupled cluster singles, doubles, and perturbative triples (CCSD(T)) theory along with the embedded fragmentation method. The proposed algorithm is capable of performing large-scale calculations using high-level wavefunction theories, and accurately describing covalent, ionic, hydrogen bonding, and dispersion interactions within molecular crystals, and therefore can predict the crystal structures, Raman spectra and phase transition of solid ammonia phases I and IV accurately. We confirm the crystal structures of solid ammonia phases I and IV that have been controversial for a long time and predict their phase transition that occurs at 1.17 GPa and 210 K with small temperature dependence, which is in line with experiment.