[CPMD-list] About getting surface energy in CPMD

[Hong Won Keon]

Hi, CPMD-lists,

 

I'm struggling with getting surface energy on Pt(111) surface.

 

I've searched many places to find out infos and tips on surface energy.

 

Firstly, I've found there was a CPMD tutorial in CECAM in 2002.  On
sixth day the lecture was done on surface energy. Is there anyone who
has that material - lecture notes or so? Could you share it?

 

Secondly, I've found A. Alavi's paper, who gave lecture in 2002.
According to his paper, the fundamental formula for the surface free
energy is

Sigma = 1/corresponding area * ( the total Gibbs free energy - the sum
of (chemical potential of the species*the number of atoms of each
species) )

 

But my question is how can we get this value in CPMD?

What I've found so far is The total Gibbs free energy is total energy at
zero temperature and pressure. So I think we can get it without
problems.

Chemical potential can be obtained with Geometry Optimization of bulk -
After Force Initialization.

Number of atoms is obvious.

Then how can we get corresponding area? 

 

For Pt(111) surface, I tried p(1x1) five layer(2 top layers are relaxed)
to get surface energy. The data I've got is 

Total energy of surface = -132.1071 a.u

Chemical potential of bulk = 11.1371 eV = 0.4093 a.u.

So, after calculation following the above equation, I get too large
number. 

What's wrong with my calculation or equation?

 

 

Thanks in advance,

 

Hongwk

 

     

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