ACCURACY OF DFT CALCULATIONS IN THE DISSOCIATION OF N 2 /W(110)
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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
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MOLECULAR DYNAMICS
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MOLECULAR DYNAMICS
Direct Reflection
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MOLECULAR DYNAMICS
Direct dissociative sticking
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MOLECULAR DYNAMICS
Dynamic Trapping
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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
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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)
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NORMAL INCIDENCE
PW91 RPBE
Ei = 0.4 eV, 5000 trajectories
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60o INCIDENCE
PW91 RPBE
Ei = 0.9 eV, 5000 trajectories
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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.
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THE END(Thank you for your attention!)
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BACK TO THE PES
Top
Hollow
Bridge
Long Top-Hollow