Evolutionary optimization of PAW data-sets for accurate high pressure simulations

Abstract

We examine the challenge of performing accurate electronic structure calculations at high pressures by comparing the results of all-electron full potential linearized augmented-plane-wave calculations with those of the projector augmented wave (PAW) method. In particular, we focus on developing an automated and consistent way of generating transferable PAW data-sets that can closely produce the all electron equation of state defined from zero to arbitrary high pressures.The technique we propose is an evolutionary search procedure that exploits the ATOMPAW code to generate atomic data-sets and the Quantum ESPRESSO software suite for total energy calculations. We demonstrate different aspects of its workability by optimizing PAW basis functions of some elements relatively abundant in planetary interiors. In addition, we introduce a new measure of atomic data-set goodness by considering their performance uniformity over an enlarged pressure range.

Thermodynamic properties ofε-Fe with thermal electronic excitation effects on vibrational spectra

“…The GBRV and EPAW predictions agree well with each other. EPAW reproduces better the all-electron EoS [32]. This seems to suggest that the unsatisfactory performance of these good EPAW and GBRV potentials is related to the uncertain temperature in the NIF experiments at the highest pressure.…”

“…All calculations are performed using the Mermin functional [23,25,26] as implemented in the Quantum ESPRESSO [31] software. We use several available pseudopotential and PAW datasets [32][33][34], including the Evolutionary PAW (EPAW) dataset [32] as our primary choice, to investigate the isentropic EoS of ε-Fe up to 1,400 GPa and 8,000 K. As we focus on high pressure and temperature conditions, we conduct spin-unpolarized calculations. We use the Perdew-Burke-Ernzerhof generalized-gradient-approximation (PBE-GGA) [35] for the exchange and correlation functional.…”

“…We then compute the volume/density throughout this 𝑇 − 𝑃 profile. We use three different valence-core electron interaction potentials, EPAW [32], JTH [33] and GBRV [34] to assess the impact of this approximation at very high pressures, a significant point of concern. The vibrational contribution to the free energy is computed using VDoSs calculated using the EPAW method.…”

First-principles estimation of partition functions representing disordered lattices such as the cubic phases of Li2OHCl and Li2OHBr

“…The disordered subspace analysis also allows us to estimate the corresponding number of micro-canonical configurations M of the cubic structure, which, according to Eq. (32), is found to be roughly 10 3 for 2 × 2 × 2 supercells of both Li 2 OHCl and Li 2 OHBr.…”

“…31 Some of the data sets were improved (particularly Cl) by using the method of Sarkar et al. 32 For calculations of the phonon densities of states, QUAN-TUM ESPRESSO was used to perform density functional perturbation theory calculations. 20 Several other computer packages were used in this study.…”