unable to reproduce the adsorption energy of o2 on Pd(111)

[satish]

I am trying to reproduce the adsorption energies of molecular adsorption of O2 on Pt(111) and Pd(111). However, I am getting a value of around -1.6 eV for both O2/Pt and O2/Pd while reported values are around -0.5 eV (D.C. Ford et al. DOI: 10.1016/j.susc.2010.05.026 ). I am not sure where I am going wrong. For other species like OH, H2O, CO*, etc. I get close values to published literature. I was suspecting doing something wrong with O2 molecular energy calculation. Any help is appreciated. Thank you.

Input for molecular O2 with optimized geometry:
lattice \
15 0 0 \
0 15 0 \
0 0 15

ion-species /usr/local/JDFTX/build/pseudopotentials/GBRV/pd_pbe_v1.2.uspp
ion-species /usr/local/JDFTX/build/pseudopotentials/GBRV/c_pbe_v1.2.uspp
ion-species /usr/local/JDFTX/build/pseudopotentials/GBRV/o_pbe_v1.2.uspp

coords-type cartesian #The following coordinates are in terms of lattice vectors
ion O 0.000000000000000 -0.000000000000000 -0.213715987689531 1
ion O 0.000000000000000 0.000000000000000 2.103025878352977 1

elec-initial-charge +1 -1

kpoint-folding 1 1 1 # 4x4x1 uniform k-mesh
kpoint 0 0 0 1 # gamma-centered k-point mesh

ionic-minimize \
dirUpdateScheme L-BFGS \
linminMethod DirUpdateRecommended \
nIterations 100

elec-ex-corr gga-pbe
dump ionic State Ecomponents
initial-state o2.$var
dump-name o2-t.$var

Optimized geometry (system is singlet) for O2 adsorbed Pd(111):
ion Pd 0.011478567402726 -0.008199976164384 18.683709078357868 1
ion Pd 5.212699131687938 -0.008447042253150 18.684051366657144 1
ion Pd 2.612809318789534 4.588133455208506 18.951372737344919 1
ion Pd 7.865368089218556 4.498069458998010 18.910202858884595 1
ion Pd 2.619361116787006 1.530979572486082 23.192140790046999 1
ion Pd 7.872003432504755 1.486523264902021 23.073706308954101 1
ion Pd 5.253701644800653 6.093911552788840 23.168531474618273 1
ion Pd 10.489849250244150 6.093854944825198 23.168200716925970 1
ion Pd 0.000000000000000 3.032677676900000 27.474967692000000 0
ion Pd 5.252751819399998 3.032677676900000 27.474967692000000 0
ion Pd 2.626375909690000 7.581694192289998 27.474967692000000 0
ion Pd 7.879127729089999 7.581694192289998 27.474967692000000 0
ion Pd 0.000000000000000 0.000000000000000 31.763821593099998 0
ion Pd 5.252751819399998 0.000000000000000 31.763821593099998 0
ion Pd 2.626375909690000 4.549016515359999 31.763821593099998 0
ion Pd 7.879127729089999 4.549016515359999 31.763821593099998 0
ion O 1.353745934875411 0.011497329673343 15.026265571336406 1
ion O 3.871166775024044 0.021813711575236 15.026807212059980 1

clean Pd(111) (system is singlet):
ion Pd 0.001133993695504 0.000533789831417 18.844544426078443 1
ion Pd 5.252361243945849 0.000565350497393 18.845465596565621 1
ion Pd 2.626739999156962 4.548463601266543 18.845177786959503 1
ion Pd 7.879494560339793 4.549332257047250 18.845650056680132 1
ion Pd 2.626261943528277 1.517164390735213 23.164783121900410 1
ion Pd 7.879824255180066 1.517232051316700 23.166412824631692 1
ion Pd 5.253049103268729 6.065052648171344 23.166013322640111 1
ion Pd 10.505807511798329 6.064572590927022 23.166056602450436 1
ion Pd 0.000000000000000 3.032677676910000 27.474967692000000 0
ion Pd 5.252751819389999 3.032677676910000 27.474967692000000 0
ion Pd 2.626375909689999 7.581694192279998 27.474967692000000 0
ion Pd 7.879127729079999 7.581694192279998 27.474967692000000 0
ion Pd 0.000000000000000 0.000000000000000 31.763821592999999 0
ion Pd 5.252751819389999 0.000000000000000 31.763821592999999 0
ion Pd 2.626375909690000 4.549016515369999 31.763821592999999 0
ion Pd 7.879127729079999 4.549016515369999 31.763821592999999 0

Eadsorption=27.2*(-1567.70268645517-(-31.9795292316109-1535.66151193186))=-1.6 eV

[Ravishankar Sundararaman]

Did you specify "spintype z-spin" for the O2 molecule calculation?

(Giving two entries in initial charge does not automatically set this.)

Cheers,
Shankar

[satish]

It matches now :) Thanks a lot :)