A New High-Pressure Polar Phase of Crystalline Bromoform: A First-Principles Study

Abstract

The high-pressure phases of bromoform at zero temperature have been investigated by first-principles pseudopotential plane-wave calculations based on the density functional theory. A new high-pressure polar phase, ε, with space group CC has been found after a series of simulated annealing and geometry optimizations. Our calculated enthalpies showed that the transition from β phase to γ phase occurs at 1 GPa, then the γ phase transforms to the ε phase at 90 GPa. In addition, the Br···Br and C-H···Br interactions are the key factors for the polar aggregation in the ε phase. Further calculations show that the insulate-metal transition in ε phase due to band overlap happens at ~130 GPa.

Structure, elasticity and stability of reidite (ZrSiO4) under hydrostatic pressure: A density functional study

“…However, the enthalpy calculation (see Section 3.3) indicates that reidite is likely to occur as a thermodynamically metastable phase at pressures <7.3 GPa, where zircon is the most stable phase. The wolframite type phase also satisfies the Born criterion for monoclinic systems [43]. At pressures >75.8 GPa, wolframite is the stable polymorph, but reidite would occur as a metastable phase.…”

Structural, electronic, and optical properties of crystalline iodoform under high pressure: A first-principles study

“…Moreover, it is observed that nonpolar symmetry to polar symmetry transformation took place in the bromoform and chloroform. 26,27 Therefore, the polar structure is perhaps favorable for crystalline haloform under high pressure. The calculated lattice parameters at 50 GPa for β-CHI 3 are a = 9.1303 Å, b = 5.5213 Å, c = 10.8126 Å, and β = 147.54 • .…”

“…In addition, the calculated metallization pressure of 32 GPa for CHI 3 is lower than that of 130 GPa for crystalline CHBr 3 in our early work. 27 The metallization pressure shows an attractive decrease with increment of halogen radius. This trend is well correlated with both the electronegativity of halogen and bandgap of halogen at ambient pressure.…”

“…23,25 Several studies have reported the significant effect of pressure on enhancing molecular aggregates and controlling the strength of C-H · · · X (X = F, Cl, Br, and I) and halogen · · · halogen interactions. 24,26,27 To obtain further information about pressure effect on weak interactions of C-H · · · X and halogen · · · halogen, we study the polyhalomethane iodoform at various pressures by means of first-principles calculations. The purpose of this work is based on previous investigations, including our experimental and theoretical works on iodoform, to study electronic structure, optical properties, the intermolecular interactions of iodoform, and to explore its structures phase transition at high pressures by means of density-functional theory (DFT) up to 150 GPa.…”

Phase Stability of Chloroform and Dichloromethane at High Pressure

“…The only exception is iodoform (CH 3 I) which was studied by powder X-ray diffraction up to 40 GPa, and by Raman spectroscopy up to 22 GPa [27]. Computational studies on the high-pressure transformations of crystals containing tri-and dihalomethane are also scarce, with only CHBr 3 and CHI 3 investigated [38,39]. Table 1.…”