Large Volume Collapse during Pressure-Induced Phase Transition in Lithium Amide

Abstract

The structural studies of lithium amide (LiNH2) have been performed by synchrotron X-ray diffraction measurements and ab initio density functional theoretical calculations up to 28.0 GPa. It is revealed that LiNH2 undergoes a reversible pressure-induced phase transitions from tetragonal phase (I-4) into the monoclinic phase (P21), which starts from about 10.3 GPa and completes at about 15.0 GPa. This transition is accompanied by about 11% large volume collapse, and this volume collapse is much larger than other complex ternary hydrides. The experimental pressure–volume data for the two phases of LiNH2 are fitted by third-order Birch–Murnaghan equation of state, yielding B 0 of 37.2 (1.7) GPa for the tetragonal phase and 7.6 (4.9) GPa for the monoclinic phase with the pressure derivatives at 3.5. We also have calculated the total and partial density of states of the two phases in order to explore the mechanism of the volume reduction.

A Novel High-Density Phase and Amorphization of Nitrogen-Rich 1H-Tetrazole (CH2N4) under High Pressure

“…These obvious phenomena reveal that a crystalline-to-crystalline transition occurs at 3.1 GPa then completes at 7.8 GPa. The coexistence region from 3.1 to 7.8 GPa is largely caused by slow transition kinetics 22 23 24 . At 7.8 GPa, the sample is fully converted into a new phase, and no structural changes are observed in the XRD profiles up to ~11 GPa.…”

Materials by design at high pressures

“…6). [116][117][118][119][120][121][122] Extensive experiments have been performed to investigate the polymerization of nitrogen in azides, and the dissociation of double N]N bonds was only observed in NaN 3 considering the disappearance of molecular vibrations above 120 GPa. 123 However, polymerization of nitrogen has not been observed in other azides, as the experimental pressures considered for other azides are lower than 50 GPa.…”

Shock Wave Induced Switchable Phase Transition (Molecular Distortion Type) of Ammonium Sulfate Crystal

“…However, still there are lots of fundamental aspects to be unearthed as to how speci c changes are enforced in materials with respect to their crystallographic structural features at high-pressure and high-temperature conditions [1][2][3][4][5]. Moreover, some of the materials show stable crystallographic con guration even at a considerably high pressure of GPa range [6,7] whereas a few materials undergo reversible [8][9][10][11] and irreversible [12,13] phase transitions during pressure compression and decompression. Hence, it has become increasingly ubiquitous prospect for researchers to understand better the basic concepts of structural phase transition of materials under external stimuli conditions [14,15].…”