Introducing PROFESS: A new program for orbital-free density functional theory calculations

We present PROFESS (PRinceton Orbital-Free Electronic Structure Software), a new software package that performs orbital-free density functional theory (OF-DFT) calculations. OF-DFT is a first principles quantum mechanics method primarily for condensed matter that can be made to scale linearly with system size. We describe the implementation of energy, force, and stress functionals and the methods used to optimize the electron density under periodic boundary conditions. All electronic energy and potential terms scale linearly while terms involving the ions exhibit quadratic scaling in our code. Despite the latter scaling, the program can treat tens of thousands of atoms with quantum mechanics on a single processor, as we demonstrate here. Limitations of the method are also outlined, the most serious of which is the accuracy of state-of-the-art kinetic energy functionals, which limits the applicability of the method to main group elements at present. Program summary: Program title: PROFESS. Catalogue identifier: AEBN_v1_0. Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBN_v1_0.html. Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland. Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html. No. of lines in distributed program, including test data, etc.: 35 933. No. of bytes in distributed program, including test data, etc.: 329 924. Distribution format: tar.gz. Programming language: Fortran 90. Computer: Intel with ifort; AMD Opteron with pathf90. Operating system: Linux. RAM: Problem dependent, but 2 GB is sufficient for up to 10,000 ions. Classification: 7.3. External routines: FFTW (http://www.fftw.org), MINPACK-2. Nature of problem: Given a set of coordinates describing the initial ion positions under periodic boundary conditions, recovers the ground state energy, electron density, ion positions, and cell lattice vectors predicted by orbital-free density functional theory. Except for computation of the ion-ion and ion-electron terms, all other terms are effectively linear scaling. Up to ∼10,000 ions may be included in the calculation on just a single processor. Solution method: Computes energies as described in text; minimizes this energy with respect to the electron density, ion positions, and cell lattice vectors. Restrictions: PROFESS cannot use nonlocal (such as ultrasoft) pseudopotentials. Local pseudopotential files for aluminum, magnesium, silver, and silicon are available upon request. Also, due to the current state of the kinetic energy functionals, PROFESS is only reliable for main group metals and some properties of semiconductors. Running time: Problem dependent: the test example provided with the code takes less than a second to run. Timing results for large scale problems are given in the paper. References:. [1] Y.A. Wang, N. Govind, E.A. Carter, Phys. Rev. B 58 (1998) 13465;. Y.A. Wang, N. Govind, E.A. Carter, Phys. Rev. B 64 (2001) 129901 (erratum). [2] S.C. Watson, E.A. Carter, Comput. Phys. Comm. 128 (2000) 67.