[CPMD-list] problem designing SiO2 slab

[Axel Kohlmeyer]

On Mon, 21 Feb 2005, Younes Ansari wrote:

dear younes,

YA> dear sir:
YA>     I have designed a slab of quartz and I want to know if there isn`t any  problem with it.
YA>     The SiO2 volume is 290 A' so it wont be any problems to have 
YA> CELL
YA>     10.000   1.0   1.0  0  0.0  
YA> Because if I chage it to 11.00 or more the program wont be run . 

why not? also, if this is a slab, your x- and y- (or more precise
a and b/a values) are predetermined by the size of your unit cell and
only the c/a value can be changed arbitrarily. you should also
make sure, that you 'cut the slab properly', i.e. you don't have
a dipole across the slab in z-direction, or else you will be in 
biiiiiig trouble. ;-)

YA>  I have an other problem beacause my programs do not mach with the
YA> tutorial that Dr. Kohlmayer have made. for example..

so does your input. you are just confirming one of my previous suspicions.

YA>  
YA> WAVEFUNCTION
YA>  
YA> &CPMD
YA>     OPTIMIZE WAVEFUNCTION
YA>     INITIALIZE WAVEFUNCTION
YA>     .
YA>     .
YA>   if i dont use the INITIALIZE WAVEFUNTION in CPMD 3-9-1 my program wont run even in GEOMETRY OPTIMIZATION and MOLECULAR DYNAMICS CP. So is there a problem with the input files.
YA> NOTE: The tutorial of theochem wont be run unless I chage it to INITIALIZE WAVEFUNCTION.

that is not correct. you need to set INITIALIZE WAVEFUNCTION to either
RANDOM or ATOMIC or it will be ignored. your error is, that you don't
provide a numeric argument to TRAJECTORY _in_ the _next_ line,
so you will trigger a problem there. please examine your output file
closely. there should be some 'UNRECOGNIZED KEYWORDS' messages there.

also, if you start a molecular dynamics run, you _have_ to start
from a preconverged wavefunction, the only exception being, that
you want to use simulated annealing to optimize the wavefunction,
but that is rarely called for.

so you first do a run with OPTIMIZE WAVEFUNCTION and then
another with MOLECULAR DYANMICS CP _and_ 
RESTART WAVEFUNCTION COORDINATES LATEST

axel.


-- 

=======================================================================
Dr. Axel Kohlmeyer   e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.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/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.