The PseudoDojo: Training and grading a 85 element optimized norm-conserving pseudopotential table

Abstract

First-principles calculations in crystalline structures are often performed with a planewave basis set. To make the number of basis functions tractable two approximations are usually introduced: core electrons are frozen and the diverging Coulomb potential near the nucleus is replaced by a smoother expression. The norm-conserving pseudopotential was the first successful method to apply these approximations in a fully ab initio way. Later on, more efficient and more exact approaches were developed based on the ultrasoft and the projector augmented wave formalisms. These formalisms are however more complex and developing new features in these frameworks is usually more difficult than in the norm-conserving framework. Most of the existing tables of normconserving pseudopotentials, generated long ago, do not include the latest developments, are not systematically tested or are not designed primarily for high accuracy. In this paper, we present our PseudoDojo framework for developing and testing full tables of pseudopotentials, and demonstrate it with a new table generated with the ONCVPSP approach. The PseudoDojo is an open source project, building on the AbiPy package, for developing and systematically testing pseudopotentials. At present it contains 7 different batteries of tests executed with ABINIT, which are performed as a function of the energy cutoff. The results of these tests are then used to provide hints for the energy cutoff for actual production calculations. Our final set contains 141 pseudopotentials split into a standard and a stringent accuracy table. In total around 70.000 calculations were performed to test the pseudopotentials. The process of developing the final table led to new insights into the effects of both the core-valence partitioning and the non-linear core corrections on the stability, convergence, and transferability of norm-conserving pseudopotentials. The PseudoDojo hence provides a set of pseudopotentials and general purpose tools for further testing and development, focusing of highly accurate calculations and their use in the development of ab initio packages. The pseudopotential files are available on the PseudoDojo web-interface www.pseudo-dojo.org in the psp8, UPF2, and PSML 1.1 formats.

Implementation and Validation of Fully RelativisticGWCalculations: Spin–Orbit Coupling in Molecules, Nanocrystals, and Solids

“…To understand our sources of error, we first performed computations with a number of different pseudopotentials at the DFT level, followed by further computations at the GW level. Details of these computations, and of the other pseudopotentials used, 88,122,123,133,158,159 are given in the SI. In Table 18 GaAs, and Zn compounds show variation between different pseudopotentials derived with the same valence partition.…”

Materials design of dynamically stable d9 layered nickelates

“…The phonon calculations of the 57 layered nickelates were performed by computing second-order interatomic force constants with sufficiently large supercells. For quickly identifying dynamically stable compositions of the 1214 and 1213 families, we started the phonon calculations with 2×2×2 supercells, which contain 64 (56) atoms for the 1214 (1213) family. For each nickelate, the dynamical stability is assessed from the presence of unstable phonon modes; if an unstable phonon mode (ω 2 qν < 0) exists on the commensurate 2×2×2 q points, the composition is dynamically unstable and therefore excluded from the candidate list.…”

Emergent dual topology in the three-dimensional Kane-Mele Pt2HgSe3

“…Structural optimization is performed by using the experimental lattice parameters as obtained from X-ray diffraction and relaxing the atomic coordinates with a non-local van der Waals functional, namely the vdW-DF2 functional [38] with C09 exchange (DF2-C09) [39], and the SSSP precision pseudopotential library v1.0 [40] with 100 Ry of wavefunction cutoff and a dual of 8. Further calculations on the optimized crystal structure (band structures and Wannier functions) are performed using the PBE functional [41] and ONCV [42] scalar and fully relativistic pseudopotentials from the PseudoDojo library [43] with 80 Ry of wavefunction cutoff and a dual of 4. All calculation are perfomed with k-point density of 0.09Å −1 , that corresponds to a k−point grid of 12 × 12 × 14, and Marzari-Vanderbilt smearing [44] of 0.015 Ry.…”