The ABINIT Users Mailing List ( CLOSED )

[Tianjiao Zhang <tjzhang@quantumstates.com>]

Hi,
(1)As you have the variation of the total energy(Graphite + OH)vs the 
distance between the Oxygen and Carbon,
where is the location of the minimum ?
(2) As the carbons in plane form bonds like  2HC=CH2,  and especially 
with C atoms replacing H, you may expect stronger
volume repulsion occured to O than that  in CH3. Is the surface energy 
still positive at larger C-O distance ?
Can your C in C-O do some out of layer relaxation ?  Does C-O-H have to 
form a 180 degree bond ?
Just as the case of HOH, molecules not necessarily following symmetry we 
generously impose in solid state physics.
Sincerely,
Tianjiao

okuno@osa.sci.jri.co.jp wrote:

> Dear Abinit Users.
>
> I use Abinit for estimation of  the bond length of the HO-C length of the Graphite surface 
> with its C atom is terminated by OH group, the distance between O atom of OH group and  
> C atom of the graphite,  because Graghite in the solvant is always 
> terminated by some functional group like OH.
>
> We assume OH group density on the Graphite surface is very tiny, 
> (we do not know this assumption is right), and set one sheet of Graphite 
> in the unit  cell with 24 atoms and set OH group on the top of one Carbon atom. 
>
> We calculate surface energy by E(Graphite + OH) -E(OH) -E(Graphite) 
> (where E(x) is x's total energy) with changing the distance between  the Oxygen 
> and Carbon.
>
> But the results shows the energy minimum of the surface energy is located the 
> distance 6.5Bohr, and when the case of the distance 2.5Bohr (the distance of 
> CH3-OH) the results show positive surface energy and indicate the OH group 
> are not absorbed by Graphite. 
>
> Are there some need for attention to treat the functional group like OH?
>
>
> Our input file for the Graphite(one sheet with 24 atoms and one OH group)
> is like below.
>
>
>
> nsppol 2
>
> #Definition of the unit cell
> acell      13.9235010838      16.0774741976      25.3072104390
> rprim     1.000000000000     0.000000000000     0.000000000000
>          0.000000000000     1.000000000000     0.000000000000
>          0.000000000000     0.000000000000     1.000000000000
> ntypat    3 
> znucl 1 6 8 
> natom   26 
> typat 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 1 
> xcart 
>    0.000000000000     0.000000000000     0.000000000000 
>    2.320583513975     1.339789516470     0.000000000000 
>    2.320583513975     4.019368549411     0.000000000000 
>    0.000000000000     5.359158065882     0.000000000000 
>    0.000000000000     8.038737098823     0.000000000000 
>    2.320583513975     9.378526615293     0.000000000000 
>    2.320583513975    12.058105648234     0.000000000000 
>    0.000000000000    13.397895164704     0.000000000000 
>    4.641167027950     0.000000000000     0.000000000000 
>    6.961750541925     1.339789516470     0.000000000000 
>    6.961750541925     4.019368549411     0.000000000000 
>    4.641167027950     5.359158065882     0.000000000000 
>    4.641167027950     8.038737098823     0.000000000000 
>    6.961750541925     9.378526615293     0.000000000000 
>    6.961750541925    12.058105648234     0.000000000000 
>    4.641167027950    13.397895164704     0.000000000000 
>    9.282334055900     0.000000000000     0.000000000000 
>   11.602917569875     1.339789516470     0.000000000000 
>   11.602917569875     4.019368549411     0.000000000000 
>    9.282334055900     5.359158065882     0.000000000000 
>    9.282334055900     8.038737098823     0.000000000000 
>   11.602917569875     9.378526615293     0.000000000000 
>   11.602917569875    12.058105648234     0.000000000000 
>    9.282334055900    13.397895164704     0.000000000000 
>    4.641167027950     5.359158065882     2.500000000000 
>    4.641167027950     5.359158065882     4.500000000000 
>
> tsmear 0.04 
> kptopt 1
> ngkpt 1 1 1 
> ecut 60 
> nstep 50 
> toldfe 1.0d-6 
>
>
>
> Y. OKuno 
> Japan Research Institute.
>
>
>