From NWChem

Contents 1 DPLOT 1.1 GAUSSIAN -- Gaussian Cube format 1.2 TITLE -- Title directive 1.3 LIMITXYZ -- Plot limits 1.4 SPIN -- Density to be plotted 1.5 OUTPUT -- Filename 1.6 VECTORS -- MO vector file name 1.7 WHERE -- Density evaluation 1.8 ORBITAL -- Orbital sub-space 1.9 Examples 1.9.1 Charge Density 1.9.2 Molecular Orbital

DPLOT

 DPLOT
   ...
 END

This directive is used to obtain the plots of various types of electron densities (or orbitals) of the molecule. The electron density is calculated on a specified set of grid points using the molecular orbitals from SCF or DFT calculation. The output file is either in MSI Insight II contour format (default) or in the Gaussian Cube format. DPLOT is not executed until the "task dplot" directive is given. Different sub-directives are described below.

The implementation of the dplot functionality uses mostly local memory. The quantities stored in local memory are:

• the positions of the grid points
• the property of interest expressed at the grid points

The stack memory setting in the input file must be sufficient to hold these quantities in local memory on a processor.

GAUSSIAN -- Gaussian Cube format

 GAUSSIAN

A outputfile is generate in Gaussian Cube format. You can visualize this file using gOpenMol (after converting the Gaussian Cube file with gcube2plt), Molden or Molekel.

TITLE -- Title directive

 TITLE <string Title default Unknown Title>

This sub-directive specifies a title line for the generated input to the Insight program or for the Gaussian cube file. Only one line is allowed.

LIMITXYZ -- Plot limits

 LIMITXYZ [units <string Units default angstroms>]
 <real X_From> <real X_To> <integer No_Of_Spacings_X>
 <real Y_From> <real Y_To> <integer No_Of_Spacings_Y>
 <real Z_From> <real Z_To> <integer No_Of_Spacings_Z>

This sub-directive specifies the limits of the cell to be plotted. The grid is generated using No_Of_Spacings + 1 points along each direction. The known names for Units are angstroms, au and bohr.

SPIN -- Density to be plotted

 SPIN <string Spin default total>

This sub-directive specifies, what kind of density is to be computed. The known names for Spin are total, alpha, beta and spindens, the last being computed as the difference between α and β electron densities.

OUTPUT -- Filename

 OUTPUT <string File_Name default dplot>

This sub-directive specifies the name of the generated input to the Insight program or the generated Gaussian cube file. The name OUTPUT is reserved for the standard NWChem output.

VECTORS -- MO vector file name

 VECTORS <string File_Name default movecs> [<string File_Name2>]

This sub-directive specifies the name of the molecular orbital file. If the second file is optionally given the density is computed as the difference between the corresponding electron densities. The vector files have to match.

WHERE -- Density evaluation

 WHERE <string Where default grid>

This sub-directive specifies where the density is to be computed. The known names for Where are grid (the calculation of the density is performed on the set of a grid points specified by the sub-directive LimitXYZ and the file specified by the sub-directive Output is generated), nuclei (the density is computed at the position of the nuclei and written to the NWChem output) and g+n (both).

ORBITAL -- Orbital sub-space

 ORBITALS [<string Option default density>]
 <integer No_Of_Orbitals>
 <integer Orb_No_1 Orb_No_2 ...>

This sub-directive specifies the subset of the orbital space for the calculation of the electron density. The density is computed using the occupation numbers from the orbital file modified according to the Spin directive. If the contours of the orbitals are to be plotted Option should be set to view (instead of the implicit default value density). Note, that in this case No_Of_Orbitals should be set to 1 and sub-directive Where is automatically set to grid. Also specification of two orbital files conflicts with the view option. alpha orbitals are always plotted unless Spin is set to beta.

Examples

Charge Density

Example of charge density plot (with Gaussian Cube output):

start n2
geometry
  n  0 0   0.53879155
  n  0 0  -0.53879155
end
basis;  n library cc-pvdz;end
scf
vectors  output n2.movecs
end
dplot
  TITLE HOMO
  vectors n2.movecs
   LimitXYZ
 -3.0 3.0 10  
 -3.0 3.0 10 
 -3.0  3.0  10
  spin total
  gaussian
  output chargedensity.cube
end
task scf     
task dplot

Molecular Orbital

Example of orbital plot (with Insight II contour output):

start n2
geometry
  n  0 0   0.53879155
  n  0 0  -0.53879155
end
basis;  n library cc-pvdz;end
scf
vectors  output n2.movecs
end
dplot
  TITLE HOMO
  vectors n2.movecs
   LimitXYZ
 -3.0 3.0 10  
 -3.0 3.0 10 
 -3.0  3.0  10
  spin total
  orbitals view; 1; 7
  output homo.grd
end
task scf     
task dplot