The structural phase transition of ammonia borane under high pressure. (27th November 2020) - Shi, Lan-Ting
Abstract: We have systematically studied the high-pressure (up to 100 GPa) behavior of ammonia borane at 0 K using particle optimization algorithm combined with the first principles calculation. The long-unsolved high-pressure structures and a complete phase transition sequence were obtained: P63 mc → Pmn21 → P21 (Z = 2) → P21 (Z = 4) → C2/m → P21 /m, and the phase transition pressures are 1.23, 2.77, 11.9, 13.8, 22.34 GPa, respectively. The lack of imaginary phonon frequency effectively proves the rationality and dynamic stability of the above structures. The Raman modes calculated by density functional theory (DFT) reveals the evolution of the vibration mode under pressure, which is in good agreement with the experiment results. The analysis of dihydrogen bonds in ammonia borane shows the bonding mechanism of different high-pressure phase structures. Our research not only enriches the high-pressure phase structure of the ammonia borane system but also provides essential information for hydrogen storage materials. Graphical abstract: Image 1 Highlights: The high-pressure phase structures by structure search. A complete phase transition sequence of ammonia borane at high pressure. The structures of the experiment were confirmed by the comparison of Raman spectra.