Improving the efficiency of FP-LAPW calculations

Abstract

The full-potential linearized augmented-plane wave (FP-LAPW) method is well known to enable most accurate calculations of the electronic structure and magnetic properties of crystals and surfaces.The implementation of atomic forces has greatly increased its applicability, but it is still generally believed that FP-LAPW calculations require substantial higher computational effort compared to the pseudopotential plane wave (PPW) based methods.In the present paper we analyse the FP-LAPW method from a computational point of view.Starting from an existing implementation (WIEN95 code), we identified the time consuming parts and show how some of them can be formulated more efficiently. In this context also the hardware architecture plays a crucial role. The remaining computational effort is mainly determined by the setup and diagonalization of the Hamiltonian matrix. For the latter, two different iterative schemes are compared. The speed-up gained by these optimizations is compared to the runtime of the "original" version of the code, and the PPW approach. We expect that the strategies described here, can also be used to speed up other computer codes, where similar tasks must be performed. Nature of the physical problemFor ab-initio studies of the electronic and magnetic properties of poly-atomic systems, such as molecules, crystals, and surfaces. Method of solutionThe full-potential linearized augmented plane wave (FP-LAPW) method is well known to enable accurate calculations of the electronic structure and magnetic properties of crystals [1,2,3,4,5,6,7,8,9,10,11]. Within the supercell approach it has also been used for studies of defects in the bulk and for crystal surfaces.

Optical properties of armchair (7, 7) single walled carbon nanotubes

“…The optical properties of (7, 7) CNTs were simulated within the density functional theory (DFT) framework applying generalized gradient approximation (PBE-GGA) [27][28][29] Kohn-Sham equations. The calculations have been performed using WIEN2k code.…”

Metastable precursors during the oxidation of the Ru(0001) surface

“…Our DFT calculations employ the generalized gradient approximation (GGA) of the exchange-correlation functional 4 , using the full-potential linear augmented plane wave method (FP-LAPW) [5][6][7] to solve the KohnSham equations. The Ru(0001) surface is modeled using a slab with six metal layers for oxygen coverages up to two monolayers (ML) and a 10 metal layer slab for higher coverages.…”

Surface core-level shifts at an oxygen-rich Ru surface: O/Ru(0001) vs. RuO2(110)

“…The full-potential linear augmented plane wave method (FP-LAPW) [17][18][19] is used to solve the Kohn-Sham equations. We model the O(1 × 1)/Ru(0001) surface with a six layer slab, adsorbing O on both sides to preserve mirror symmetry.…”