Static, dynamic, and electronic properties of liquid gallium studied by first-principles simulation

Abstract

First-principles molecular dynamics simulations having a duration of 8 ps have been used to study the static, dynamic and electronic properties of ℓ-Ga at the temperatures 702 K and 982 K. The simulations use the densityfunctional pseudopotential method and the system is maintained on the Born-Oppenheimer surface by conjugate gradients relaxation. The static structure factor and radial distribution function of the simulated system agree very closely with experimental data, but the diffusion coefficient is noticeably lower than measured values. The long simulations allow us to calculate the dynamical structure factor S(q, ω). A sound-wave peak is clearly visible in S(q, ω) at small wavevectors, and we present results for the dispersion curve and hence

Ensemble Density-Functional Theory forAb InitioMolecular Dynamics of Metals and Finite-Temperature Insulators

“…As a paradigmatic case we present here results for a unit cell that is 32Å long, and contains a 15-layer 1×1 Al(110) slab. We use the single k-point 2π a0 ( 1 4 , 1 4 , 1 4 ), a fictitious Gaussian temperature [13] the temperature assures that the coarse sampling is sufficient; similar results are obtained with smaller and more physical temperatures. Fig.…”

“…Fig. 1 monitors the convergence of the total free energy and of the Hellmann-Feynman forces as a function of the number of iterations on the {ψ i }; we compare an optimal all-bands variational implementation (ABV) [13] with the scheme that we have described (ensemble-DFT) [14]. The improved convergence for the total energies, and particularly for the HellmannFeynman forces, is clearly apparent.…”

Dynamical and transport properties of liquid gallium at high pressures

“…17, the resulting pressure is negative by a few GPa. The MSD displacement converges slowly with system size compared to the convergence of the pressure.…”

“…Fig. 4 shows the correlation function and the mean square displacement at ambient density (ρ =6 g/cm 3 ) and a temperature T = 1000 K for which both experimental data [33] and previous ab initio calculations [17] are available. The pair correlation function agrees nicely with previous ab initio and MEAM calculations.…”

“…For gallium, this method has previously been applied [17] to study the properties of the liquid phase at ambient density (6.09 g/cm 3 ) for temperatures below 1000 K. Using a limited number of atoms (e.g., 64) in the simulation supercell and a limited k-point grid, the method reproduced the structure of the liquid and the experimental DC conductivity while the experimental diffusion coefficient was underestimated by a factor of two. The present study builds on this previous work by reporting simulations where both the convergence of supercell and k-point grid sizes were investigated, and by simulations performed along the principal Hugoniot up to a pressure of 150 GPa.…”