KGEC: Kubo-Greenwood Electrical Conductivity

The first public version of our package to calculate Kubo-Greenwood electrical conductivity now is available. KGEC is a post-processor to QuantumEspresso. QE versions 5.1.2, 5.2.1, 5.4.0, 6.0, and 6.1 currently are supported. QE 5.2.1 compiled for use in our PROFESS@QuantumEspresso suite [see below!] also is supported. KGEC provides calculation of the full complex conductivity tensor and has options for both the original KG formula (with Lorentzian) or the delta-function approximation (with both Gaussian and Lorentzian approimations for the delta function). Inter-band, intra-band, and degenerate-state contributions are calculated. The code is MPI-parallelized with respect to k-points, bands, and plane waves and has a scheme to recover plane-wave processes for use in the bands parallelization.

The preprint of the paper submitted to Computer Physics Communications is on our Publications page. That paper should be cited for KGEC.

We encourage you to explore KGEC. Links to the down-loadable tarball and Guide for implementation and basic testing are at the right. Our software is provided under GNU GPL. We welcome your comments and suggestions.

PROFESS@Quantum-Espresso

Update (23 June 2017): we've made a minor revision so that QuantumEspresso 5.2.1 prepared for use with PROFESS@QuantumEspresso also will work with KGEC [see above]. No other changes are involved. The version 2.0.1 tarball is available from the link at the right.

With pleasure we announce version 2 of PROFESS@QuantumEspresso (02 March 2016). It enables the OFDFT code PROFESS to drive ab initio MD in QuantumEspresso. The new version uses PROFESS 3.0 and QuantumEspresso 5.2.1. The package includes our T-dependent non-interacting and exchange-correlation single-point functionals, as additions to both PROFESS and QuantumEspresso (XC functionals). The tarball also now contains a short list of known problems. If you discover any others, please let us know.

Please download and try the package. Links to the down-loadable tarball and README (implementation and basic testing) are at the right. Our software is provided under GNU GPL. For convenience, we will maintain the links to version 1 of PROFESS@QuantumEspresso for about six months, then archive that software.

Links to the PROFESS and QuantumEspresso websites are farther down on the right, under DFT Codes. To use PROFESS@QuantumEspresso, you must download those codes and comply with their respective licenses.

Details of PROFESS@QuantumEspresso are described in an article, "Finite-temperature orbital-free DFT molecular dynamics: coupling PROFESS and Quantum Espresso", Computer Phys. Commun. 185, 3240 (2014). The reprint is available from the Publications page. That paper should be cited for all references to PROFESS@QuantumEspresso. Other references are given in the README.

PROFESS@QuantumEspresso is installed on the Univ. Florida Research Computing system called HiperGator. There is a brief Wiki summary.

LSDA Exchange-Correlation Free Energy Subroutines

Local Download A tarball and README for our subroutines to evaluate the LSDA exchange-correlation free energy functional are available from the links at the right. This is the KSDT functional which we built by fitting to path-integral Monte Carlo data. See Phys. Rev. Lett. 112, 076403 (2014) on Publications page. Please cite that paper if you use these subroutines. They are essentially the KSDT free energy subroutines in PROFESS@Quantum-Espresso; see above. As usual, licensure is under GNU GPL.

LibXC Initialization The LibXC implementation of KSDT has an odd limitation. If initialized in the standard LibXC way, the default is zero temperature. At right, we provide initialization routines in both Fortran and C, tests, and a HOWTO file explaining usage.

Fermi-Dirac Integral Combination Analytical Fits

Certain combinations of Fermi-Dirac integrals occur so often that it is computationally effective to have analytical representations of them. Some of the older fits are not adequate to contemporary needs, especially as regards their derivatives (for which those fits usually were not designed). Here we provide Fortran-90 subroutines to evaluate several of those combinations and their derivatives with high accuracy. Links to the README and downloadable tarball are to the right. Our software is provided under GNU GPL.

The fitting scheme and numerical tests are discussed in "Improved Analytical Representation of Combinations of Fermi-Dirac Integrals for Finite-temperature Density Functional Calculations", Computer Phys. Commun. 192, 114-123 (2015) The reprint is available from our Publications. That paper should be cited for all references to the F-D integral fits software.

Downloadable Pseudopotentials and PAWs

The links at the right provide downloads of the transferable pseudopotentials and projector augmented wave data sets which we have developed for H, Li, and Al in WDM conditions. The reference papers (see Publications Publications) are Phys. Rev. B 86, 115101 (2012) and Phys. Rev. E 86, 056704 (2012). Please cite them in publications which use these pseudopotentials and PAWs.

Plane-wave basis Kohn-Sham codes typically use non-local pseudopotentials. Those have different potentials for different angular momentum KS orbitals. OFDFT has no KS orbitals, so a local pseudopotential is necessary.

Transferability refers to how well the pseudopotential, usually generated for a free atom, works in a different environment, for example a solid or molecule. In WDM, both the temperature and material density push the limits of transferability. Part of our technical work is to develop both local and non-local pseudopotentials that are temperature and material density transferable for the WDM regime.

DFT Codes

We have used several different DFT codes for functional development and WDM research. Our primary codes at present are PROFESS and QuantumEspresso. See PROFESS@Quantum-Espresso, above. Links to websites for both, as well as to other codes are at the right.

The primary requirement for using an orbital-based code at finite-T is to have fractional occupations of eigenstates implemented with a Fermi-Dirac distribution. Many codes have this implemented, as it long has been known that use of a smearing function aids in scf convergence for metallic systems. However, such implementations may not have been tested in the WDM temperature-density domain.

KGEC

PROFESS@Quantum-Espresso

LSDA Exchange-Correlation Free Energy Subroutines

Fermi-Dirac Integral Combination Fits

Pseudopotentials & PAWs

DFT Codes