compass

Compass is used to do some preprocessing of the user's input. The main task of compass is to read molecule geometry and basis set and store them as internal data structure. The point group symmetry of molecule could be determined automatically and symmetry information will be generated.

General keywords

Basis

The following line is a string to specify the basis set name used in calculation. This string is used to locate the file in which basis set are stored. In general, there is a file with the name of capital "string" in the directory basis_library of BDF main directory. Except for the directory basis_library, the work directory will also be searched to locate the basis set. Thus, users can write the basis set into a file with the name of "NAME" in work directory and specify in input file.

Examples:

$Compass
Basis
 cc-pvdz
Geometry
  H  0.000   0.000    0.707
  H  0.000   0.000   -0.707
End of Geometry
$End

RI-J/RI-K/RI-C

Define auxiliary basis sets used in RI calculation. RI-J: Coulomb fitting. RI-K: exchange fitting, RI-C: correlation fitting.

Examples:

$Compass
Basis
 DEF2-SVP
RI-J
 DEF2-SVP
Geometry
  H  0.000   0.000    0.707
  H  0.000   0.000   -0.707
End of Geometry
$End

Geometry

The cartesian coordinates of a molecule are written as following lines with the format of

• Atom x y z

The string "End of geometry" is used to specify the end of the geometry input. The "xyz" formatted file can also be used as molecule geometry input. Users can write molecule geometry into a file named "test.xyz" (if your input file named test.inp, the input geometry should be stored in test.xyz using standard xyz format) and put it in work directory. The compass will read molecule geometry from this file.

Examples:

$Compass
Basis
  cc-pvdz
Geometry
  H  0.000   0.000    0.707
  H  0.000   0.000   -0.707
End of Geometry
$End

Geometry is read from a file named bdftask.xyz

$Compass
Basis
  cc-pvdz
Geometry
  XYZ
End of Geometry
$End

Geometry is read as internal coordinate.

$Compass
Basis
  cc-pvdz
Geometry
  zmat
O 
H 1 0.95
H 1 0.95 2 109.0
End of Geometry
$End

Group

The following line is used to set the point group of the molecule used in calculation. Usually, the point group can be determined by BDF automatically. However, the point group with degenerated representation is only supported by BDF in HF/DFT/TDDFT calculations. In general, D2h and subgroup is used by most of BDF modules. By default, BDF will use highest ablian group of a molecules point group in calculation if use do not set "Skeleton" keyword. Users can specify the subgroup of molecule point group in calculation.

For Abelian group symmetries, the numbering of irreps is

Examples:

A linear molecule CO has the Cinfv linear symmetry. We can use highest albeilian subgroup in calculation

$Compass
Basis
  sto-3g
Geometry
  C   0.0   0.0    0.0
  H   0.0   0.0    1.6
End of Geometry
Group
  C(2v)
$End

Nosymm

This keyword is used to turn off the molecule symmetry in calculation.

Norotate

Disables rotation to standard orientation. Mandatory for QM/MM.

Unit

This keyword is use to set unit of input coordinate. "Bohr" is for atomic unit. "Angstrom" is for angstrom. The angstrom is used for default.

Examples:

$Compas
Basis
  cc-pvdz
Geometry
  H  0.000   0.000    1.5
  H  0.000   0.000  -1.5
End of Geometry
Unit
 Bohr
$End

Skeleton

This keyword ask the skeleton matrix method is used in calculation. The symmetry adapted integral will not be generated and the symmetry independent integrals will be used to calculate the skeleton Fock/J/K matrices in calculation. The integral direct SCF and post-HF calculation use this method in calculation. The none-abelian group can be used in calculation when Skeleton is asked.

Example:

A CH4 molecule has the Td symmetry, we can use Td group in SCF calculation.

$Compass
Title
 CH4 Molecule test run, 3-21G
Basis
 3-21G
Geometry
 C   0.000000   0.000000   0.000000
 H   0.617765   0.617765   0.617765
 H  -0.617765  -0.617765   0.617765
 H  -0.617765   0.617765  -0.617765
 H   0.617765  -0.617765  -0.617765
End geometry
Skeleton
$End

Extcharge

Define type of external charge in calculation. A file with name bdftask.extcharge should be put into work directory to input charges and coordinates. Value should be point and gaussian.

$COMPASS
Title
 H2 Molecule test run, 3-21G
Basis
 cc-pvdz
Geometry
 H 0.000  0.000     0.70018162
 H 0.000  0.000   -0.70018162
 X 0.000  0.000     0.80018162
 X 0.000  0.000   -0.80018162
 X 0.000  0.000     0.60018162
 X 0.000  0.000   -0.60018162
End geometry
Check
Unit
 Bohr
nosymm
ExtCharge
 Point
$END

Expert keywords

Uncontract

This keyword asks to use primitive GTOs instead of contracted ones.

Prim

This keyword asks to read primitive GTOs from a specific basis file. In the basis file, ncont must equal to nprim and the contraction coefficients are not provided.

Kratzer

Non-adibatic diatom molecule calculation. Next line is used to specify the parameters of Kratzer potential. Three integers and two floats are needed.

$COMPASS 
Title
 H2 Molecule test run, 3-21G
Basis
 cc-pvdz
Geometry
 H 0.000  0.000     0.70018162
 H 0.000  0.000   -0.70018162
 X 0.000  0.000     0.80018162
 X 0.000  0.000   -0.80018162
 X 0.000  0.000     0.60018162
 X 0.000  0.000   -0.60018162
End geometry
Check
Unit
 Bohr
nosymm
Kratzer
# maxnu maxj ngausslag re         de
 10   0   50 1.40036324  0.365148      
$END