accuracy of dft calculations in the dissociation of n 2 /w(110)

ACCURACY OF DFT CALCULATIONS IN THE DISSOCIATION OF N2/W(110)

G.A. Bocan, R. Díez Muiño, M. Alducin, H.F. Busnengo, and A. Salin

Donostia International Physics Center (DIPC) San Sebastián, Spain

MOLECULAR DYNAMICS

MOLECULAR DYNAMICS

Direct Reflection

MOLECULAR DYNAMICS

Direct dissociative sticking

MOLECULAR DYNAMICS

Dynamic Trapping

HOW AND WHY

System: N2 / W(110) (large crystallographic anisotropies)

Build the 6D Potential Energy Surface (PES)+

Classical molecular dynamics

DFT calculations (VASP): Grid of 5610 6D points

Interpolation: Corrugation Reducing ProcedureThe PES

XC modeled by a GGA functional Adiabatic approximation Frozen surface

DFT not exact!!

Only reflection & dissociative sticking allowed

DYNAMICS: PW91 vs. RPBE

Theoretical prediction(PW91 XC functional in the PES)

Alternative RPBE XC functional Better fit to experimental

chemisorption energies Better description very

near the metallic surface Better dynamics??

Theoretical prediction

(RPBE XC functional in the PES)H.E. Pfnür et al., JCP 85 7452 (1986)C.T. Rettner et al., JCP 93, 1442 (1990)M. Alducin et al., PRL 97, 056102 (2006)

NORMAL INCIDENCE

PW91 RPBE

Ei = 0.4 eV, 5000 trajectories

60o INCIDENCE

PW91 RPBE

Ei = 0.9 eV, 5000 trajectories

CONCLUSIONS

The differences between RPBE and PW91 results are a measure of the PES DFT calculation accuracy.

RPBE higher medium distance barriers make it more difficult for incoming trajectories to reach the precursor well, thus ensuring a better fit to experiments in normal incidence but also a poor prediction for the 60o incidence case.

THE END(Thank you for your attention!)

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