[Pw_forum] High adsorption energies: CO on Ni-111

Elliot Menkah elliotsmenkah at yahoo.com
Sun Dec 13 19:31:21 CET 2015


Hello Everyone,
In trying to validate the computational methods and configuration of my
system for a desired study, the adsorption energies I obtained upon
computation seems to be about twice the value of what i was expecting.

This is adsorption of CO on nickel surface sites on Ni-111 surface
structure.
Literature mentions the adsorption energies on the sites top, bridge,
fcc and hcp to be: -137.9, -159.0, -163.7 and -164.6 kJ/mol
respectively,  whereas i'm getting -305.03, -328.04, -339.56 and -409.55
kJ/mol respectively.

The qualitative trend seems to exists  where the hcp site is the most
energetically favourable site for adsorption in both literature and my
study, however, quantitatively, my values are too larger.

I adsorb the molecule on only one side of the slab.

Do I have to adsorb on both sides of the slab in mirror positions to
handle dipole moment perpendicular to the surface due to adsorption?


What could the reason or problem be?

Please find attached the input files of my hcp site calculation for your
perusal.

Thank you.

Kind Regards,
Elliot


 

-- 
Elliot S. Menkah, AMRSC 
Research Student - Computational Chemistry/ Computational Material Science
Theoretical and Computational Chemistry
Dept. of Chemistry
Kwame Nkrumah UNiversity of Sci. and Tech.
Kumasi
Ghana

Tel: +233 243-055-717

Alt Email: esmenkah at knust.edu.gh
           elliotsmenkah at gmail.com
           elliotsmenkah at hotmail.com



-------------- next part --------------
&CONTROL
       title = 'Ni-2x2-111-6L-MD-CO-3fold-fcc' ,
       calculation = 'relax' ,
       restart_mode = 'from_scratch' ,
       outdir = './tmp' ,
       pseudo_dir = '/home/eliot/pseudo' ,
       prefix = 'ni-111-2x2-6L-MD-CO-3fold-fcc',
       tstress = .true. ,
       tprnfor = .true. ,
/
 &SYSTEM
       ibrav = 0,
       celldm(1) = 1.88972599,
       nat = 98,
       ntyp = 3,
       ecutwfc = 40,
       ecutrho = 480,
       occupations='smearing',
       smearing='mp',
       degauss=0.05,
       nbnd=560,
       nspin=2,
       starting_magnetization(1)=0.5,
/
 &ELECTRONS
        conv_thr = 1.0D-6,
        mixing_mode = 'local-TF'
/
 &IONS
/
ATOMIC_SPECIES
        Ni 58.6934   Ni.pbe-nd-rrkjus.UPF
         C 12.011     C.pbe-rrkjus.UPF
         O 15.999     O.pbe-rrkjus.UPF
ATOMIC_POSITIONS (alat)
Ni       1.245247692   0.718944090   0.015868783    0   0   0
Ni       2.490495415   2.875776414   0.015868783    0   0   0
Ni       3.735743138   0.718944090   0.015868783    0   0   0
Ni       4.980990830   2.875776397   0.015868355    0   0   0
Ni       1.245247472   3.594720360   2.023998778    0   0   0
Ni       2.490495415   5.751553065   2.023998778    0   0   0
Ni       3.735743358   3.594720360   2.023998778    0   0   0
Ni       4.980990830   5.751552793   2.023999431    0   0   0
Ni       1.245247844   6.470496971   4.059965132    0   0   0
Ni       2.490495415   8.627329032   4.059965132    0   0   0
Ni       3.735742986   6.470496971   4.059965132    0   0   0
Ni       4.980990830   8.627329190   4.059964979    0   0   0
Ni       1.246709841   9.346680057   6.089903308
Ni       2.491049866  11.503272365   6.094695989
Ni       3.736309279   9.347499400   6.091839589
Ni       4.981632933  11.503215624   6.094592854
Ni       1.251397606  12.222515270   8.130528230
Ni       2.493872076  14.374876735   8.130574795
Ni       3.736773669  12.222408715   8.121452049
Ni       4.979701257  14.375516889   8.129406603
Ni       1.243830060  15.097651794  10.124780901
Ni       2.490567863  17.254288878  10.125834084
Ni       3.737277529  15.124361083  10.124533866
Ni       4.983701851  17.254644423  10.125942272
Ni       3.735743107   5.032608685   0.015868783    0   0   0
Ni       4.980990830   7.189441009   0.015868783    0   0   0
Ni       6.226238553   5.032608685   0.015868783    0   0   0
Ni       7.471486245   7.189440992   0.015868355    0   0   0
Ni       3.735742887   7.908384955   2.023998778    0   0   0
Ni       4.980990830  10.065217660   2.023998778    0   0   0
Ni       6.226238773   7.908384955   2.023998778    0   0   0
Ni       7.471486245  10.065217388   2.023999431    0   0   0
Ni       3.735743259  10.784161566   4.059965132    0   0   0
Ni       4.980990830  12.940993627   4.059965132    0   0   0
Ni       6.226238401  10.784161566   4.059965132    0   0   0
Ni       7.471486245  12.940993785   4.059964979    0   0   0
Ni       3.736296794  13.660278999   6.094631584
Ni       4.981840953  15.816305949   6.089805212
Ni       6.225869615  13.659635984   6.091567601
Ni       7.472468264  15.816767005   6.089493887
Ni       3.736896631  16.534686190   8.122356924
Ni       4.983572283  18.693711643   8.122423344
Ni       6.227530794  16.536159378   8.121678221
Ni       7.475062891  18.697174708   8.130314215
Ni       3.737430863  19.413420133  10.125793472
Ni       4.981744277  21.571270847  10.124719443
Ni       6.205422793  19.399131231  10.125043022
Ni       7.471688751  21.569920708  10.195553976
Ni       6.226238522   0.718944090   0.015868783    0   0   0
Ni       7.471486245   2.875776414   0.015868783    0   0   0
Ni       8.716733968   0.718944090   0.015868783    0   0   0
Ni       9.961981660   2.875776397   0.015868355    0   0   0
Ni       6.226238302   3.594720360   2.023998778    0   0   0
Ni       7.471486245   5.751553065   2.023998778    0   0   0
Ni       8.716734188   3.594720360   2.023998778    0   0   0
Ni       9.961981660   5.751552793   2.023999431    0   0   0
Ni       6.226238674   6.470496971   4.059965132    0   0   0
Ni       7.471486245   8.627329032   4.059965132    0   0   0
Ni       8.716733816   6.470496971   4.059965132    0   0   0
Ni       9.961981660   8.627329190   4.059964979    0   0   0
Ni       6.225973474   9.346546538   6.089989264
Ni       7.471621945  11.503853546   6.089790972
Ni       8.717377404   9.346452757   6.090683436
Ni       9.963257320  11.503913751   6.089966258
Ni       6.222932962  12.222252478   8.129332507
Ni       7.470857119  14.378343414   8.121361647
Ni       8.718059007  12.222626174   8.121568843
Ni       9.964518686  14.378185126   8.121779387
Ni       6.230847493  15.098640938  10.124112763
Ni       7.474569271  17.253185302  10.124621946
Ni       8.718011778  15.098252280  10.124628469
Ni       9.961558698  17.252773665  10.124595778
Ni       8.716733937   5.032608685   0.015868783    0   0   0
Ni       9.961981660   7.189441009   0.015868783    0   0   0
Ni      11.207229383   5.032608685   0.015868783    0   0   0
Ni      12.452477075   7.189440992   0.015868355    0   0   0
Ni       8.716733717   7.908384955   2.023998778    0   0   0
Ni       9.961981660  10.065217660   2.023998778    0   0   0
Ni      11.207229603   7.908384955   2.023998778    0   0   0
Ni      12.452477075  10.065217388   2.023999431    0   0   0
Ni       8.716734089  10.784161566   4.059965132    0   0   0
Ni       9.961981660  12.940993627   4.059965132    0   0   0
Ni      11.207229231  10.784161566   4.059965132    0   0   0
Ni      12.452477075  12.940993785   4.059964979    0   0   0
Ni       8.717314947  13.660636235   6.089490100
Ni       9.962110380  15.816726745   6.089592695
Ni      11.208740061  13.659631527   6.091948135
Ni      12.452767496  15.816182474   6.090053196
Ni       8.717575346  16.537924157   8.121748080
Ni       9.960512304  18.696990663   8.130311275
Ni      11.207967602  16.535790646   8.121816703
Ni      12.452489216  18.693540783   8.122210426
Ni       8.718626602  19.409894146  10.195007369
Ni       9.966868016  21.570687486  10.192425525
Ni      11.231381306  19.398971630  10.124254459
Ni      12.455857855  21.571478700  10.123984004
C        8.723467559  20.851726334  11.508948792
O        8.727741803  20.853291675  12.699898222
K_POINTS automatic
  5 5 1   0 0 0
CELL_PARAMETERS
+9.9619816602  +0.0000000000  +0.0000000000
 +4.9809908302  +8.6273291898  +0.0000000000
 -0.0000000000  +0.0000000000 +24.2008859472
 


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