Ab initiomolecular dynamics study of pressure-induced phase transition in ZnS

Abstract

The pressure-induced phase transition in zinc sulfide is studied using a constant-pressure ab initio technique. The reversible phase transition from the zinc-blende structure to a rock-salt structure is successfully reproduced through the simulations. The transformation mechanism at the atomistic level is characterized and found to be due to a monoclinic modification of the simulation cell, similar to that obtained in SiC. This observation supports the universal transition state of high-pressure zinc-blende to rock-salt transition in semiconductor compounds. We also study the role of stress deviations on the transformation mechanism and find that the system follows the same transition pathway under nonhydrostatic compressions as well.

Ab initio molecular dynamics simulation of structural transformation in zinc blende GaN under high pressure

“…The AIMD simulations performed by Durandurdu [18] showed that the lattice structure is simultaneously compressed along the [0 1 0] direction and elongated along the other directions, which leads to the onset of a phase transformation in SiC. The ZB → RS transformation mechanism in ZnS obtained from the same method [19] is also different from the case of GaN. For ZnS, it was observed that upon structural transformation a simultaneous compression along the [0 1 0] direction and an expansion along the other directions initially occur, and then theˇangle changes gradually, resulting in a monoclinic modification of the simulation cell [19].…”

“…In our previous study on the high-pressure induced phase transi- tion from hexagonal wurtzite to the rocksalt structure in both SiC and GaN [11], the transition pressures of MD simulations were also much larger than those predicted by first-principle calculations. In Parrinello-Rahman simulations it is generally observed that the transformation does not proceed by nucleation and growth, but instead it occurs across the entire simulation cell [19]. This leads to the system crossing a significant energy barrier to transform from one phase to another one, and the simulation box being overpressurized in order to obtain a phase transition within the accessible simulation time [36,37].…”

“…3. Gen- erally, the modification of the simulation cell during the phase transformation can provide a clear picture of the transformation mechanism at the microscopic level [11,13,[17][18][19]. In Fig.…”

“…The ZB → RS transformation mechanism in ZnS obtained from the same method [19] is also different from the case of GaN. For ZnS, it was observed that upon structural transformation a simultaneous compression along the [0 1 0] direction and an expansion along the other directions initially occur, and then theˇangle changes gradually, resulting in a monoclinic modification of the simulation cell [19]. In our previous study on the high-pressure induced wurtzite to rocksalt structural transition in GaN [11], we have demonstrated that the WZ → RS phase transformation undergoes inhomogeneous displacements via a tetragonal atomic configuration.…”

“…Recently, ab initio MD method (AIMD) has been employed to investigate the highpressure induced phase transition in zinc blende semiconductors [11,[17][18][19][20][21][22], which has proved to be an invaluable tool to understand the microscopic transformation mechanisms at the atomic level. The constant-pressure ab initio MD simulations performed on SiC [18,22], ZnS [19], ZnSe [20] and AlN [21] suggested that the pressure-induced ZB → RS phase transition is based on tetrahedral (space group: I4m2) and orthorhombic (space group: Imm2) intermediate states, differing from the previous first-principles and MD simulation results, in which no tetragonal intermediate state has been observed.…”