Scope

VASP [1] is a highly efficient ab initio method for structural optimizations, ab initio molecular dynamics (MD), and the calculation of electronic and magnetic properties. It is applicable to solids, interfaces, surfaces, molecules on surfaces, and isolated molecules. It covers all elements of the periodic table of practical interest. With its carefully tested library of projector-augmented-wave (PAW) potentials, VASP combines the accuracy of all-electron methods with the elegance and computational efficiency of plane-wave approaches. Within MedeA, VASP automatically computes heats of formation of compounds using a precomputed database of all elements in their standard reference states.

Features

• All-electron projector-augmented-wave (PAW) potentials covering all atoms of the periodic table of practical interest
• Generalized gradient approximation (GGA) and local density approximation (LDA)
• Spin-polarized and spin restricted
• Semi-relativistic and full spin-orbit relativistic
• Non-collinear magnetism
• LDA (GGA)+U for correlated systems
• Applicable to bulk systems, surfaces, interfaces, and molecules (in supercell geometry)
• Total energies, forces, and the full stress tensor
• Concurrent relaxation of lattice parameters and atomic positions
• Ab initio molecular dynamics
• Generation of Monkhorst-Pack special k-points
• Integration in k-space with smearing or tetrahedron method (with Blöchl correction)
• Band structure (spin restricted and spin polarized)
• Site, spin and partial-wave projected densities of states
• Atom-projected charges decomposed into s, p,d and f-components
• Total and atom-projected magnetic moments
• Ultra-soft pseudopotentials for comparison with other calculations

Examples

Zirconia

The lattice parameters, internal atom positions, and total energies are computed for the low-temperature monoclinic phase and the high-temperature tetragonal and cubic phases of zirconia. The computed structural parameters are within 1.3 % of their experimental values.This structural information is obtained within a few minutes of computing time, thus demonstrating MedeA-VASP as a powerful and efficient source of structural data. The ranking of the total energies reflects the observed trend of the monoclinic phase being the most stable at low temperatures, followed by the tetragonal, and the high-temperature cubic phases. Total energies from accurate VASP calculations provide a sound starting point for calculations of thermodynamic properties.

Reconstruction of a Silicon Carbide Surface

The computation with MedeA-VASP of the structure of a silicon-rich SiC(001) surface provides detailed insight into the (3x2) reconstruction, which involves the formation and tilting of surface silicon dimers (see figure on the right).

Using a 54-atom supercell model, a full geometry optimization was performed in less than 2 hours on a 2-processor computer.

MedeA-VASP is being used by a number of leading research groups as illustrated, for example, by the study of the adsorption of thiophene on a MoS2 surface [2] and by the investigation of the adhesion of aluminum to diamond-coated surfaces [3].

Spin-orbit Relativistic Bands of a III-V Semiconductor

VASP 4.6 allows the computation of fully spin-orbit relativistic energy band structures. An example is AlSb, where relativistic spin-orbit effects lead to significant changes in the valence band (see figure below).

References

1. G. Kresse and J. Furthmüller, Phys. Rev. B 54, 11169 (1996); Computat. Mat. Sci. 6, 15 (1996)
2. P. Raybaud, J. Hafner, G. Kresse, and H. Toulhoat, Phys. Rev. Lett. 80, 1481 (1998)
3. Y. Qi and L. G. Hector, Phys. Rev. B 68, 201403 (2003)