Vienna ab initio simulations package

The density functional calculations were performed using the Vienna Ab Initio Simulation Package (VASP). ° The spin-polarized generalized gradient approximation, Perdue—Wang exchange correlation function, and ultrasoft pseudopotentials were used. ... 

The Vienna Ab Initio Simulation Package (VASP) program33,34 was developed to carry out calculations to obtain the fluctuation trajectory of the selected models. The VASP program uses a rather traditional self-consistency scheme to evaluate the instantaneous electronic ground-state at each molecular dynamics (MD) step so that the wavefunction can be converged to the Born-Oppenheimer surface at each time-step. 

The experiments at the Pohang Accelerator Laboratory were supported in part by MOST and Pohang Iron and Steel (POSCO). Special thank to Isao Tanaka for supporting the ab initio total-energy and molecular dynamics program VASP (Vienna ab initio simulation package). 

The Vienna Ab Initio Simulation Package (VASP) has been used to perform the periodic structure calculationsAll atoms have been allowed to relax completely within the periodic unit cell. The large 12-membered ring Mordenite has been used for this study as this zeolite has a relatively small unit cell (i.e. 146 atoms). It has previously been studied by Demuth et al. . For our zeolite model, the Si/Al ratio is 23, and the geometry of the unit cell is described by a = 13.648 k, b = 13.672 A, c = 15.105 A, a = 96.792 >5 =... 

The main codes for periodic DFT calculations differ by the choice of basis sets. There are three possibilities atomic orbitals (CRYSTAL, SIESTA, GAUSSIAN codes), plane waves (Vienna ab initio simulation package (VASP), CASTEP, DACAPO, CPMD, Quantum-ESPRESSO codes), or both with a partition of the space between atomic spheres and intermediate regions (APW, LMTO, KKR, WIEN2K codes). We will shortly describe the advantage and disadvantage of the two extreme choices taking CRYSTAL and VASP as representative codes. 

Figure 3.6 shows a possible 3D molecular arrangement of a Zn " cation surrounded by six H2O molecules. The structure was optimized by performing first-principles periodic density functional calculations using projector-augmented wave (PAW) potentials [23, 24] for describing electron-ion interactions, within the Vienna Ab initio Simulation Package (VASP) software [25]. 

VASP the Vienna ab initio simulation package is designed for quantum mechanical MD using DFT and HF methods. 

Based on the same underlying principles as the molecular-based quantum methods, solid state quantum mechanics represents bulk material using periodic boundary conditions. The imposition of these boundary conditions means that it becomes possible to expand the electron density in periodic functions such as plane waves, as an alternative to the atom-based functions used in the molecular case. The efficiency of the calculations is enhanced by the use of pseudo-potentials to represent the core electrons and to make the electron density as smooth as possible near the nucleus, hence reducing the complexity of the plane wave expansion of the electron density. Because of the number of choices available for pseudo potentials, basis sets and whether calculations are done in real or reciprocal space, there are many choices of software for performing solid state quantum mechanical calculations. A few examples which have been used in crystal structure prediction include the Vienna ab initio Simulation Package (VASP), CASTEP and CRYSTAL. " A wider ranging introduction to the area can be found in the references. ... 

Vienna ab initio Simulation Package (VASP) (Kresse and FurethmuUer 2000), and Car-Parrinello MD Program (CAMP-Atami) (Ohnishi 1994) combine molecular dynamics with DFT under a periodic boundary condition with the orbitals expanded in the plane wave. They have been routinely used in industrial applications such as heterogeneous catalysis. 

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