[CPMD-list] About the CELL keyword

[Ari P Seitsonen]

Dear John,

  i) 2.802 = 3.962/sqrt(2) = the nearest-neighbour distance in the (111)
plane of the fcc lattice.

  ii) 3.93 is probably the calculated/optimised lattice constant of
aluminium, slightly smaller than in experiments. It sounds a bit too
small, 3 % smaller than experimentally, though.

    Greetings from Zurich,

       apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
 Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
 Tel +41 1 635 44 97 / Fax +41 1 635 68 38 / GSM +41 79 719 09 35      
 Anschrift: Physikalisch Chemisches Institut (PCI), Universität Zürich (UniZh)
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 Address:   Schweiz / Svizzera / Suisse / Svizra / Switzerland

On Sun, 20 Jun 2004, John Kofi Dogbe wrote:

> Hi All,
> 
> Please, I have the following questions about the parameters for the CELL
> keyword in two input files given in the examples:
> 
> (i) Input file=pth.in --> Pt(111) slab, 3 slabs + 4 layers of vacuum:
> CELL
> 2.802    1.0    5.7155     1.0  1.0  1.0  (alat=3.962, c/a=7*sqrt(2/3)
> ? What's alat? I know it is not the lattice constant for Pt (a=3.923
> angstroms = 7.4051 a.u) and what about the a=2.802 for the CELL keyword
> for instance?
> 
> (ii) Input file=al001geo.inp--> Al(001) slab, 6 slabs + 6 layers of vacuum:
> CELL
> 2.779    1.0    8.4853   0.0 0.0 0.0 (a=3.93/sqrt(2) A, 8.4853 =12/sqrt(2) )
> Same questions as above, except that I can see where 2.779 is from.
> However, a=3.93 is not clear to me since a(the lattice constant)=4.043
> angstroms for Al = 7.6316 a.u.
> 
> Thank you.
> John
> --
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