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12:32:32 PM PDT  Thu, May 2nd 2013 

Hi,
When I tried to run the example "Optimizing a unit cell and geometry for SiliconCarbide", first I got an error message to complain the lack of memory. After I increased it, the optimization converged, and got the following information
Lattice Parameters

lattice vectors in a.u. (scale by 1.000000000 to convert to a.u.)
a1=< 8.646 0.000 0.000 >
a2=< 0.000 8.645 0.000 >
a3=< 0.000 0.000 8.127 >
a= 8.646 b= 8.645 c= 8.127
alpha= 90.000 beta= 90.000 gamma= 90.000
omega= 607.4
My question is why the norm of a3 is not the same as the norm of a1. How can I force the optimization to keep the ratios between the norms of a1, a2, and a3 constant? In other words, I would like to optimization process to scale a1, a2, a3 by the same factor.
Other questions:
1. Where can I find all possible options for different directives?
"set includelattice .true." only apprars in an example input file, but not in the section of "http://www.nwchemsw.org/index.php/Release61:Toplevel#SET"
other examples: set nwpw:stress_numerical .true. #currently only numerical stresses
set nwpw:psi_nolattice .true. # turns of unit cell checking for wavefunctions
Is there any list to tell users that those parameter can be set by "set nwpw:$$" for nwpw?
2. Where can I find the refence for "task band"? I can't find any relevant reference from documentation or the paper "NWChem: A comprehensive and scalable opensource solution for large scale molecular simulations"
3. I have used LAMMPS package. The documentation of LAMMPS is pretty easy to follow. Would you mind to take a look and revise the documentation which can include references and default settings?
Thank you in advance.
Dongsheng

Edited On 2:31:02 PM PDT  Thu, May 2nd 2013 by Zhdsheng




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9:14:19 AM PDT  Sat, May 4th 2013 

http://www.nwchemsw.org/index.php/Release61:PlaneWave_Density_Functional_Theory#Unit_Cel...
The following input seems to work for me for SiC
title "SiC 8 atom cubic cell  geometry and unit cell optimization"
echo
permanent_dir ./perm
scratch_dir ./perm
start diamond
memory 950 mb
 Enter the geometry using fractional coordinates ****
geometry center noautosym noautoz print
system crystal
lat_a 4.00d0
lat_b 4.00d0
lat_c 4.00d0
alpha 90.0d0
beta 90.0d0
gamma 90.0d0
end
Si 0.50000d0 0.50000d0 0.50000d0
Si 0.00000d0 0.00000d0 0.50000d0
Si 0.00000d0 0.50000d0 0.00000d0
Si 0.50000d0 0.00000d0 0.00000d0
C 0.25000d0 0.25000d0 0.25000d0
C 0.25000d0 0.25000d0 0.25000d0
C 0.25000d0 0.25000d0 0.25000d0
C 0.25000d0 0.25000d0 0.25000d0
end
set nwpw:kbpp_ray .true.
set nwpw:kbpp_filter .true.
nwpw
ewald_rcut 3.0
ewald_ncut 8 #The default value of 1 needs to be increased for small cells
lmbfgs
xc pbe96
end
driver
clear
maxiter 40
end
set nwpw:cif_filename sic.opt # create a CIF file containing optimization history
set includestress .true. # this option tells driver to optimize the unit cell
task pspw optimize ignore
nwpw
monkhorstpack 2 2 2
end
task band optimize ignore



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