[CPMD-list] Geometry Optimization of NaAlH4

[Axel Kohlmeyer]

On Wed, 9 Jan 2008, Gopi Krishna Pha Dathara wrote:

dear phani(?),


CKPD> Dear CPMD users,
CKPD> 
CKPD> I am trying to do geometry optimization calculation of sodium aluminum
CKPD> hydride unit cell
CKPD> I am having problems specifying the coordinates of the atoms. The
CKPD> crystallographic data from ICSD database is as follows.
CKPD> 
CKPD> Unit Cell   4.99 4.99 11.07 90 90 90
CKPD> Space Group I 41/a Z
CKPD> SG Number   88
CKPD> Cryst Sys   tetragonal
CKPD> Pearson     tI24
CKPD> Wyckoff     b a
CKPD> Atom  #   OX   SITE      x           y           z           SOF      H
CKPD>   Al   1  +3    4 b   0.          0.000       0.500          1.         0
CKPD>   Na   1  +1    4 a   0.          0.000       0.000          1.         0
CKPD>   H    1  -1    16 f  0.2662      0.6084      0.0442         1.         0
CKPD> I have no idea how to specify the number of atoms in &ATOMS...&END
CKPD> section to build the unit cell
CKPD> as per the info from database.

this is in fact more an issue of being able to 
read crystallographic data properly. the data you
have only lists the atoms positions that cannot be 
created by symmetry operations. the space group defines
those and you have to create the positions from them.

please have a look at, e.g., 
http://people.sissa.it/~degironc/QE-Tutorial/tutorial_wyckoff.pdf

this is for a different plane wave pseudopotential code,
but when carefully checking the cpmd manual, you should
be able to find out how to do something similar with cpmd.

cheers,
   axel.

CKPD> Rest of my input file is

p.s.: ???? how can you have this defined (particularly
the wavefunction cutoff), when you don't even know how
to specify the atoms/pseudopotentials? also a lot of it
does not make sense in this combination. perhaps you
should start with something simpler first...

CKPD> 
CKPD> &INFO
CKPD> NaAlH4
CKPD> Optimization calculation (Unit cell).
CKPD> &END
CKPD> 
CKPD> &CPMD
CKPD> OPTIMIZE GEOMETRY
CKPD> CONVERGENCE GEOMETRY
CKPD> 2e-07
CKPD> BFGS
CKPD> HESSIAN
CKPD> ANDERSON MIXING
CKPD> 0.5
CKPD> FREE ENERGY FUNCTIONAL
CKPD> LANCZOS DIAGONALIZATION
CKPD> EMASS
CKPD> 400
CKPD> ENERGYBANDS
CKPD> MEMORY BIG
CKPD> PRINT
CKPD> 1
CKPD> PRINTENERGY ON  
CKPD> EKIN,ELECTROSTATIC,ESR,ESELF,EFREE,EBAND,ENTROPY,EPSEU,EHEP,EHEE,EHII,ENL,EXC,VXC,EGC,EBOGO
CKPD> &END
CKPD> 
CKPD> &DFT
CKPD> FUNCTIONAL GGA
CKPD> &END
CKPD> 
CKPD> &SYSTEM
CKPD> SYMMETRY
CKPD> 6
CKPD> SCALE
CKPD> CELL
CKPD> 4.9900 1 2.2184 0 0 0
CKPD> CUTOFF
CKPD> 30.0
CKPD> &END
CKPD> --
CKPD> Phani Dathar
CKPD> LONI Graduate Fellow
CKPD> Louisiana Tech University.
CKPD> 
CKPD> ----------------------------------------------------------------
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CKPD> 
CKPD> 
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CKPD> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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