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.. index::
single: Program; GRID_IT
single: GRID_IT
.. _TUT\:sec\:gridit:
:program:`GRID_IT` --- A Program for Orbital Visualization
======================================================================
.. warning::
This program requires a submodule
:program:`GRID_IT` is an interface program for calculations of molecular
orbitals and density in a set of cartesian grid points. Calculated grid
can be visualized by separate program :program:`LUSCUS` in
the form of isosurfaces.
:program:`GRID_IT` generates the regular grid and calculates amplitudes of
molecular orbitals in this net. Keywords :kword:`Sparse`,:kword:`Dense`,
:kword:`Npoints` specify the density of the grid. And keywords :kword:`ORange` (occupation range),
:kword:`ERange` (energy range), :kword:`Select` allow to select some specific orbitals to draw.
As default :program:`GRID_IT` will use grid net with intermediate quality,
and choose orbitals near HOMO--LUMO region. Note, that using keyword
:kword:`All` --- to calculate grids for all orbitals or :kword:`Dense` --
to calculate grid with very high quality you can produce a very huge
output file.
.. _TUT\:sec\:gridit_dependencies:
:program:`GRID_IT` requires the communication file :file:`RUNFILE`,
processed by :program:`GATEWAY` and any formated :file:`INPORB` file: :file:`SCFORB`,
:file:`RASORB`, :file:`PT2ORB`, generated by program :program:`SCF`, :program:`RASSCF`,
or :program:`CASPT2`, respectively. The output file :file:`M2MSI`
contains the graphical information.
Normally you do not need to specify any keywords for :program:`GRID_IT`:
the selection of grid size, as well as the selection of orbitals done automatically.
An input example for :program:`GRID_IT` is: ::
&GRID_IT
Dense
* compute orbitals from 20 to 23 form symmetry 1 and orbital 4 from symmetry 2
SELECT
1:20-23,2:4
.. compound::
:program:`GRID_IT` can be run in a sequence of other computational codes
(if you need to run :program:`GRID_IT` several times, you have to rename
grid file by using EMIL command, or by using keyword :kword:`NAME`) ::
&GATEWAY
...
&SEWARD
&SCF
&GRID_IT
NAME=scf
&RASSCF
&GRID_IT
NAME=ras
or, you can run :program:`GRID_IT` separately, when the calculation has finished. ::
&GATEWAY
&GRID_IT
FILEORB=/home/joe/project/water/water.ScfOrb
This is quite important to understand that the timing for :program:`GRID_IT`, and
the size of generated grid file depends dramatically on the targeting problem.
To get a printer quality pictures you have to use Dense grid, but in order to see the
shape of orbitals --- low quality grids are much more preferable.
The following table illustrates this dependence:
.. _tab\:grid_it_size:
============================== ======== ======== ===============
:math:`\ce{C_{24}}` molecule, 14 orbitals.
----------------------------------------------------------------
Keywords Time (s) filesize picture quality
============================== ======== ======== ===============
:kword:`Dense`; :kword:`ASCII` 188 473 MB best
:kword:`Dense` 117 328 MB best
:kword:`Dense`; :kword:`Pack` 117 41 MB below average
Default (no keywords) 3 9 MB average
:kword:`Pack` 3 1.4 MB average
:kword:`Sparse` 1.3 3 MB poor
:kword:`Sparse`; :kword:`Pack` 1.3 620 KB poor
============================== ======== ======== ===============
:program:`GRID_IT` --- Basic and Most Common Keywords
-----------------------------------------------------
.. class:: keywordlist
:kword:`ASCII`
Generate the :file:`grid` file in ASCII (e.g. to transfer to another computer),
can only be used in combination with :kword:`NoLUSCUS`
:kword:`ALL`
Generate all orbitals
:kword:`SELECT`
Select orbitals to compute
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