It is a pleasure to announce version 2 of PROFESS@QuantumEspresso (02 March 2016). This is our software that enables the OFDFT code PROFESS to drive ab initio MD in QuantumEspresso. This new version uses PROFESS 3.0 and QuantumEspresso 5.2.1. The package also includes our T-dependent non-interacting and exchange-correlation single-point functionals, implemented as additions to PROFESS and QuantumEspresso (XC functionals).
We encourage you to download and try the package. Links to the down-loadable tarball and README (for implementation and basic testing) are at the right. Our software is made available 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 websites for PROFESS and for QuantumEspresso are farther down on the right, under DFT Codes. To use our PROFESS@QuantumEspresso implementation, you must download those two codes from their own sites 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.
The tarball also now contains a short list of known problems. If you discover any others, please let us know.
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
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 functional which we obtained by fitting to high-quality path-integral Monte Carlo data. See "Accurate Homogeneous Electron Gas Exchange-correlation Free Energy for Local Spin-density Calculations", Phys. Rev. Lett. 112, 076403 (2014) on Publications. Please cite that paper if you use these subroutines. They are, except for minor changes, the LSDA XC free energy subroutines in PROFESS@Quantum-Espresso; see above. As usual, licensure is under GNU GPL.
Fermi-Dirac Integral Combination Analytical Fits
It long has been recognized that 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.
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.