[Pw_forum] cohesive energy of C60

Jose Manuel Napoles Duarte napolesd at cactus.iico.uaslp.mx
Fri Jan 12 21:30:47 CET 2007


Dear pwscf users,

I am trying to do a test pwscf calculation of fullerene C60 in a FCC 
bravais lattice. I have the reference of Saito and Oshiyama (PRL 66 ,2637 
(1991)) and that of Troullier and Martins (PRB 46,1754 (1992)) where both 
groups found a cohesive energy of 1.6 eV. However in a preliminar result I 
have found the following energy for fcc c60 with lattice parameter 
(a_0)= 26.7248  a.u. (equivalent to a_0= 14.142 Angstrom):


> grep ! c60fccgeom10.out
!    total energy              =  -683.97694515 ryd

and for the isolated molecule:

grep ! c60damp.out
     No symmetry!
!    total energy              =  -683.91687200 ryd
!    total energy              =  -683.91692937 ryd
!    total energy              =  -683.91700216 ryd
!    total energy              =  -683.91706827 ryd
!    total energy              =  -683.91702891 ryd
!    total energy              =  -683.91705256 ryd
!    total energy              =  -683.91706654 ryd
!    total energy              =  -683.91708083 ryd
!    total energy              =  -683.91707390 ryd
!    total energy              =  -683.91708201 ryd
!    total energy              =  -683.91708245 ryd
!    total energy              =  -683.91708268 ryd
!    total energy              =  -683.91708291 ryd
!    total energy              =  -683.91708326 ryd
!    total energy              =  -683.91708337 ryd
!    total energy              =  -683.91708436 ryd
!    total energy              =  -683.91708405 ryd
!    total energy              =  -683.91708381 ryd
!    total energy              =  -683.91708464 ryd
!    total energy              =  -683.91708457 ryd
!    total energy              =  -683.91708430 ryd

So giving a cohesive energy of 0.81410756 eV which I guess is about 1/2 of 
the energy reported in the references given above. I really don`t 
understend what is happening. 
The C60 molecule is set such that each axis crosses a double bond at the 
midpoint.
Below is the input file for the fcc-C60. For the isolated molecule I first 
do a damped dynamics optimization.

thanks
J. M. Napoles
PhD student
Instituto de Investigacion en Comunicacion Optica
Universidad Autonoma de San Luis Potosi
San Luis Potosi, Mexico 

/
 &control
    calculation='scf'
    restart_mode='from_scratch'
    prefix='C60fccgeom'
    pseudo_dir=' '
    outdir=' '
 /
 &system
    ibrav=2, nat=60, ntyp=1,celldm(1)=26.7247738
    ecutwfc = 50.0, ecutrho = 300.0
    occupations='smearing', smearing='methfessel-paxton', degauss=0.005
 /
 &electrons
    conv_thr =  1.0d-6
    mixing_beta = 0.5
 /
ATOMIC_SPECIES
 C 12.0107 C.pz-rrkjus.UPF
ATOMIC_POSITIONS {angstrom}
C        1.407368348  -1.169270087  -2.996352523
C        1.155000914  -2.998721394   1.414231172
C       -2.569868573   0.727048774   2.278942600
C       -1.407369748   1.169270123   2.996354503
C       -2.572934630  -0.708858874   2.281123936
C       -1.168248777  -2.993711628   1.413850706
C       -1.154999556   2.998716434  -1.414235192
C        2.569873218  -0.727045947  -2.278934183
C       -3.443475569  -0.684030397   0.000528040
C       -2.285795345  -2.567271017  -0.714319855
C       -1.411460082  -1.163183560  -2.996790774
C        2.569183053  -0.719996621   2.281933017
C        2.572942818   0.708860996  -2.281117431
C        0.691950027  -0.006743425  -3.441895530
C        0.712638046  -2.278049679   2.574700204
C       -0.712641482   2.278048778  -2.574700904
C       -0.691960543   0.006744382   3.441896564
C        2.275044288  -2.577090608  -0.713619986
C       -2.275043517   2.577094390   0.713619895
C       -1.412387498  -1.153994791   2.999932296
C       -0.723266366  -2.274967859   2.574471677
C        2.572243493   0.715908748   2.279712906
C       -3.001182866  -1.404764735  -1.159915160
C        1.155438733  -3.003036722  -1.404638851
C       -2.572239887  -0.715911865  -2.279718564
C        1.412386937   1.153998869  -2.999931150
C       -2.995166398   1.414092648  -1.164264062
C        0.722467030   2.282840618   2.567674821
C       -0.007446490  -3.440967562   0.696724153
C        3.440539698  -0.698842016   0.001593642
C       -3.440541125   0.698844548  -0.001591405
C       -1.167819674  -2.998024268  -1.404977765
C       -0.722472878  -2.282835618  -2.567674762
C        2.995170011  -1.414092306   1.164257891
C        0.723259638   2.274974525  -2.574473179
C       -1.155437472   3.003038299   1.404638985
C        3.001187729   1.404761625   1.159913217
C        1.167819111   2.998024849   1.404975960
C        2.995521908  -1.417677189  -1.158979906
C        1.168247528   2.993715403  -1.413852038
C        0.007444736   3.440964394  -0.696728588
C       -3.001537554  -1.401174161   1.163337969
C        1.406467715  -1.160078807   3.000371626
C       -0.690908691  -0.003781257  -3.442111538
C       -2.286027765  -2.565072224   0.721571219
C        3.001546058   1.401171970  -1.163329086
C       -1.406469268   1.160075629  -3.000369224
C        0.690898738   0.003779607   3.442113424
C       -2.274832893   2.574892089  -0.722292146
C        2.286031105   2.565069342  -0.721567056
C        0.007232021   3.443069261   0.686129858
C        2.285800339   2.567266719   0.714321873
C        1.411455172   1.163183237   2.996789095
C       -2.569178195   0.719996609  -2.281934935
C        3.443475635   0.684027870  -0.000523865
C       -2.995519741   1.417679476   1.158987181
C        2.274836356  -2.574893690   0.722285126
C        0.713422702  -2.285919833  -2.567457257
C       -0.713428440   2.285919456   2.567457625
C       -0.007232083  -3.443071526  -0.686134267
K_POINTS {automatic}
 6 6 6 0 0 0









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