Structure of HUMMR Input File

Basic Layout

The HUMMR program generally requires a simple text file as input. This file consists of different Input Blocks such as General, Geom etc. Each input block is to be succeeded by the End keyword. Otherwise the program will not be able to correctly parse the provided input file. Following is a sample input:

General
  CalcType SCF
  Basis def2-svp
  Charge 0
  Mult 1
End

SCF
  SCFype RHF
End

Geom
  H 0.000000 0.000000 0.000000
  H 0.000000 0.000000 0.900000
End

Tip

Indentation is not required but highly recommended to improve the readability of the input files.

Note

Comments can be added in the input file by adding #, followed by the comment.

Essential Keywords

While many of the keywords described in Complete List of Keywords are optional, the keywords of General block- CalcType, Basis, Charge and Mult should be provided for any actual quantum chemical calculation. Of course, if only orbital plots or equations are to be generated these keywords are not required.

Geom Block

A central input block for each quantum chemical calculation with HUMMR is the Geom block as it defines the molecular geometry. Each line in the Geom block needs to have 4 entries: The first one defines the identity of the desired atom by its element symbol and the other three define its position in cartesian coordinates and Angstroem (Å). Generally the program does not differentiate between upper and lower case letters.

An alternative way of entering your molecular geometry is to provide a file that contains the required info. As appears to be convention, the file should start with the number of atoms in the first line, followed by an empty line before the molecular geometry is defined as described above. For example,

12
this is benzene
 C     0.000000     0.000000     0.000000
 C     0.000000     0.000000     1.400000
 C     1.212436     0.000000     2.100000
 C     2.424871     0.000000     1.400000
 C     2.424871     0.000000     0.000000
 C     1.212436     0.000000    -0.700000
 H    -0.943102     0.000000     1.944500
 H     1.212436     0.000000     3.189000
 H     3.367973     0.000000     1.944500
 H     3.367973     0.000000    -0.544500
 H     1.212436     0.000000    -1.789000
 H    -0.813285     0.000000    -0.695318

Note

The second line of the geometry file will be completely ignored by the input parser and can therefore contain useful comments.

The name of the input file must be given in the 'Geom' block of your input file to let the program know where to find your set of coordinates. For example,

Geom
  benzene.xyz
End

In principle, it is even possible to enter one set of coordinates in the regular way and an additional set via one or multiple files. The sets will be combined in the order they are given. However, using both ways in one calculation might easily lead to confusion and is thus not recommended.

Inclusion of Point Charges

Sometimes it is useful to run calculations with additional point charges. As the name suggests, these point charges merely add electrostatic fields and carry no basis functions. In HUMMR calculation, pointcharges can be added via an additional file that is of the following structure.

 -0.834  -1.3130    0.0000   -0.0310
  0.417  -1.8700    0.7570    0.1651
  0.417  -1.8700   -0.7570    0.1651

Each line corresponds to a point charge that is identified by four numbers. The first number determines the charge while the remaining three entries fix the position (all values shall be given in Angstroem, Å). In order to be read in the name of the file that contains the point charge info has to be specified in the General block after the keyword PointChargeFileName.

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List of HUMMR Input Blocks

• General

• Geom

• SCF

• CASSCF

• CI

• ImplicitSolvation

• FormulaGenerator

• GeomOpt

• Spectra

• OrbPlot

• Integrals

The possible keywords for each block are given in Complete List of Keywords and detailed tutorials for common applications are provided in Tutorials.

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