Quantum Monte Carlo study of pressure-induced $B3-B1$ phase transition in GaAs

We have investigated the transition pressure $p_t$ of bulk GaAs from the zinc-blende ($B3$) to the rocksalt ($B1$) structure using the local-density approximation (LDA), Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA), and diffusion Monte Carlo (DMC). We took into account finite temperature effects (zero-point vibrational effects) as well as finite-size corrections. Our DMC calculation using GGA trial nodal surface supports the higher value of the transition pressure, $\sim$17 GPa, than the lower value of $\sim$12 GPa, both of which are experimentally reported values. This projection increases the transition pressure $p_t$ from DFT predictions, being of the same tendency as that for Si bulk crystal. The choice of the exchange-correlation functional in DFT was found to significantly determine the phase-transition pressure, while DMC gave more accurate results for this transition pressure.

Figure 1

GaAs structures: (a) $B3$ (zinc-blende)-GaAs structure; (b) $B1$ (rocksalt)-GaAs structure. Magenta spheres are Ga atoms and golden ones are As atoms.

Figure 2

Biases of the ground-state energies at equilibrium volumes of $B1$ (RS) and $B3$ (ZB) structures depending on the DMC time steps (dtdmc), measured from those obtained by $\text{dtdmc}=0.01$ a.u. Plot points are shifted by a tiny amount along horizontal axis just for visibility. “Mpc/Ewd” means the schemes to evaluate Coulombic interactions, model Coulomb potentials (MPCs), and Ewald scheme, respectively. “T” and “F” specify that the variational scheme in Ref. 45 ($T$-move scheme) is used (T) or not (F).

Figure 3

Energy-volume dependence (without phonon contribution) evaluated by DFT and DMC energy for $B3$ (zinc-blende; squared symbols) and $B1$ (rocksalt; circle symbols) structures of GaAs. Variation of total energy vs volume for $B3$ (zinc-blende) and $B1$ (rocksalt) structures of GaAs. The volumes with imaginary phonon frequencies are included for DFT data. Statistical error bars for QMC data shown are within the size of each symbol.

Figure 4

Energy-volume dependence of DMC energy for $B3$ (zinc-blende; squared symbols) and $B1$ (rocksalt; circle symbols) structures of GaAs. Solid lines correspond to $T=0$ K and dashed ones to $T=300$ K, both of which include phonon contributions. Black and blue lines correspond to Ewald evaluation and red and green to MPC. Statistical error bars for QMC data shown are within the size of each symbol.