# **DIRAC¶

By default DIRAC only activates the generation of the basis set (e.g. kinetic balance conditions for small component functions) and the one-electron modules. Two-electron integrals over the atomic basis functions will be calculated when needed by the job modules given below.

We recommend that you use the Dalton program package if you want to e.g. save the two-electron integrals to disk for another purpose, this is not possible with DIRAC.

## .WAVE FUNCTION¶

Activates the wave function module(s). This activates the reading of the **WAVE FUNCTION section, where the desired wave function type(s) must be specified. If you read in converged MO coefficients from the file DFCOEF and you want to skip the SCF step and proceed directly to properties or the post-SCF step, then a trick to do this is to comment out (or remove) this keyword.

## .ANALYZE¶

Activates the Hartree–Fock or Kohn–Sham analysis module. This activates the reading of the **ANALYZE section.

## .PROPERTIES¶

Activates the property module (which will call the integral module for property integrals). This activates the reading of the **PROPERTIES section.

## .OPTIMIZE¶

Activates the geometry optimization. This activates the reading of the *OPTIMIZE subsection.

## .4INDEX¶

Explicitly activates the transformation of integrals to molecular orbital basis. This activates the reading of the **MOLTRA section.

These transformed integrals are currently only used by the **RELCC, RELADC, FANOADC and LANCZOS, **POLPRP, DIRRCI – Direct CI module, and *LUCITA modules, and if one of these three modules are requested under **WAVE FUNCTION, then this flag is automatically activated unless .NO4INDEX is specified in this input module.

By default, molecular orbitals with orbital energy between -10 and +20 hartree are included, this can be modified in the **MOLTRA section.

## .NO4INDEX¶

Do not automatically activate integral transformation to molecular orbital basis if any of **RELCC, RELADC, FANOADC and LANCZOS, **POLPRP, DIRRCI – Direct CI module, and *LUCITA modules are requested under **WAVE FUNCTION.

This keyword is utilized when repeating correlated CC or CI calculations (with different parameters for instance) based on saved files after the integral transformation.

## .TITLE¶

Title line (max. 50 characters). Example:

```
.TITLE
my first DIRAC calculation
```

## .INPTEST¶

Input test - no job modules are called, only verification of DIRAC input files. It is often useful to start a new set of calculations with an input test in order to check that input file processing is correct before submitting your (long-term run) job.

## .ONLY INTEGRALS¶

Stop after the calculation of the one-electron integrals for the Hamiltonian and the one-electron integrals specified under **INTEGRALS. The integrals are written to disk.

## .MINIMI¶

Warning

documentation missing

## .XMLOUT¶

Create the output xml-file containing selected data (in development).