Designing meaningful density functional theory calculations in materials science—a primer

Abstract

Density functional theory (DFT) methods for calculating the quantum mechanical ground states of condensed matter systems are now a common and significant component of materials research. The growing importance of DFT reflects the development of sufficiently accurate functionals, efficient algorithms and continuing improvements in computing capabilities. As the materials problems to which DFT is applied have become large and complex, so have the sets of calculations necessary for investigating a given problem. Highly versatile, powerful codes exist to serve the practitioner, but designing useful simulations is a complicated task, involving intricate manipulation of many variables, with many pitfalls for the unwary and the inexperienced. We discuss several of the most important issues that go into designing a meaningful DFT calculation. We emphasize the necessity of investigating these issues and reporting the critical details.

Recent Progresses in Understanding of Co-Based Fischer–Tropsch Catalysis by Means of Transient Kinetic Studies and Theoretical Analysis

“…The chemisorption energies of the most stable configurations for the related surface species on Co (0001) are summarized in Table 1. Generalized gradient approximation (GGA) was widely used in all studies mentioned in Table 1, which performed better for magnetic surfaces, provided better geometry optimizations and yielded more exact adsorption energies [122,123]. The chemisorption energies of the same species is slightly different from various sources since different functional (i.e.…”

Zinc surface complexes on birnessite: A density functional theory study

“…In the present case, hydrated Zn surface complexes were geometry-optimized via total energy and force minimization to provide detailed structural and electronic information about their stable groundstates. Density functional theory using plane-wave basis sets and periodic boundary conditions subject to Bloch's Theorem (Payne et al, 1992;Segall et al, 2002) is especially well-positioned to achieve accurate results for layer-type minerals through careful convergence tests performed by systematically varying the DFT components [e.g., kinetic energy cutoff, Brillouin zone sampling, and supercell size (Mattsson et al, 2005)]. Furthermore, since a plane-wave basis set treats empty space the same as it does the atoms on a lattice, defect structures such as Mn(IV) vacancies are described without structural bias.…”

The DFT+U: Approaches, Accuracy, and Applications

“…This additive term, namely the exchange and correlation (xc), is founded on approximations that have the responsibility to recover the exact energy description of the system. This approximated xc functional is a function of the electronic charge density of the system, and the accuracy of a DFT calculation is strongly dependent on the descriptive ability of this functional of the energy of the system [2]. It is generally difficult to model the dependence of the xc functional on electronic charge density, and thus, it can inadequately represent the many-body features of the N-electron ground state.…”

“…The generally used DFT-GGA failed to predict the high spin of the five coordinate Fe complexes [68], but it could be obtained by the DFT+U with U~ 4 eV and J~ 1 eV. The complexes Fe(phen) 2 (NCS) 2 and Fe(btr) 2 (NCS) 2 were tested using a U value of 2.5 eV [62], with the energy difference between the low spin state and high spin state is in agreement with the experimental values and proved that the U coulomb term was needed. The study showed the importance of magneto elastic couplings through the correlation between the spin state and the structure [62].…”

“…Density functional theory (DFT) is one of the most convenient computational tools for the prediction of the properties of different classes of materials [1,2]. Although its accuracy is acceptable as long as structural and cohesive properties are concerned, it dramatically fails in the prediction of electronic and other related properties of semiconductors up to a factor of 2.…”