[CPMD-list] geometry optimization

[Axel Kohlmeyer]

On Thu, 6 May 2004, Ðñ¶« ÌÆ wrote:

X> hi,
X> 
X> I used CPMD to run the Al slab sample in the package, which uses 
X> norm-conserving pseudopotential (AL_SGS). I got the same results as sample 
X> gives. Compared with their initial position, the inter-layer distance 
X> between two most outside layers increases around 0.125(angstrom).
X> 
X> Then I try to use Vanderbilt USPP. I modify the input file and do the 
X> calculation again. This time I find the results are quit different from the 
X> last one. The inter-layer distance between two most outside layers increases 
X> around 3.442(angstrom) !!!!
X> 
X> I guess there must be something wroing with my input file. Any suggestion?

hi,

there are two problems:
a) you need k-points
b) you need the free energy functional

you need a) to have a proper k-space sampling or you have to
use a much larger (8x8x1=64 times) supercell and you need
b) to treat the metal properly. your results therefore must be bogus.

IIRC, a) and b) are not supported with vanderbilt 
pseudopotentials (well, i am sure about a), i have not looked into b)
yet), so you're out of luck.

  axel kohlmeyer.

X> 
X> Thanks.
X> 
X> Xudong
X> 
X> -------------------------------------------------------------------------------------------------------------------------------------------
X> &CPMD
X>   OPTIMIZE GEOMETRY
X>   MEMORY BIG
X>   CONVERGENCE
X>     1.0e-4  1.0e-4
X>   SPLINE POINTS
X>     1001
X>   STRUCTURE BONDS ANGLES
X> &END
X> 
X> &DFT
X>   NEWCODE
X>   EXCHANGE CORRELATION TABLE NO
X>   FUNCTIONAL PBE
X>   GC-CUTOFF
X>     5.0e-5
X> &END
X> 
X> &SYSTEM
X>    ANGSTROM
X>    POINT GROUP
X>     AUTO
X>    SYMMETRY
X>     8
X>    CELL
X>     2.779    1.0    8.4853   0.0 0.0 0.0   (a=3.93/sqrt(2) A, 8.4853 
X> =12/sqrt(2) )
X>    CUTOFF
X>     50.0
X>    SCALE
X> &END
X> 
X> &ATOMS
X> *013-Al-gpw-n-campos.uspp NEWF BINARY
X>    LMAX=D
X>    6
X>    0   0     0
X>    1/2  1/2  1/12
X>    0   0     2/12
X>    1/2  1/2  3/12
X>    0   0     4/12
X>    1/2  1/2  5/12
X> &END
X> -------------------------------------------------------------------------------------------------------------------------------------------
X> 
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X> 

-- 


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Dr. Axel Kohlmeyer                        e-mail: axel.kohlmeyer at rub.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
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