# **GENERAL¶

## .DIRECT¶

Direct evaluation of two-electron integrals for Fock matrices (all two-electron integrals for other uses, e.g. CI, CCSD, MCSCF, are always evaluated directly, i.e. never read from disk).

The default is to evaluate LL, SL, and SS integrals directly (1 = evaluate directly; 0 = do not evaluate directly):

```
.DIRECT
1 1 1
```

## .SPHTRA¶

Transformation to spherical harmonics embedded in the transformation to orthonormal basis; totally symmetric contributions are deleted.

The default is a spherical transformation of large and small components, respectively (1 = on; 0 = off):

```
.SPHTRA
1 1
```

The transformation of the large components is a standard transformation from Cartesian functions to spherical harmonics. The transformation of the small components is modified, however, in accordance with the restricted kinetic balance relation.

## .PCMOUT¶

Write MO coefficients to the formatted file DFPCMO. This is useful for porting coefficients between machines with different binary structure. For reading the DFPCMO file, there is no keyword - simply copy this file to the working directory.

## .ACMOUT¶

Write coefficients in C1 symmetry to the unformatted file DFACMO.

## .ACMOIN¶

Import coefficients in C1 symmetry from the unformatted file DFACMO to current symmetry. This assumes that the current symmetry is lower than the symmetry used for obtaining the original coefficients.

## .LOWJACO¶

Use Jacobi diagonalization in the Löwdin orthogonalization procedure (subroutine LOWGEN). This is much slower than the default Householder method but does not mix AOs in the case of block-diagonal overlap matrix.

## .DOJACO¶

Use the Jacobi method for matrix diagonalization (currently limited to real matrices). The default Householder method is generally more efficient, but may mix degenerate eigenvectors of different symmetries.

## .QJACO¶

Employ pure Jacobi diagonalization of quaternion matrixes. Properly handles degenerate eigenvectors. Slower than .DOJACO and exclusive. Experimental option.

## .LINDEP¶

Thresholds for linear dependence in large and small components; refer to the smallest acceptable values of eigenvalues of the overlap matrix. The default is:

```
.LINDEP
1.0D-6 1.0D-8
```

## .RKBIMP¶

Import SCF coefficients calculated using restricted kinetic balance (RKB) and
add the UKB component (all small component). This option is a nice way to get
(unrestricted) magnetic balance in response calculations involving a uniform
magnetic field (e.g. NMR shielding and magnetizability), in particular when
combined with London orbitals, which makes the magnetic balance *atomic*.

## .PRJTHR¶

RKBIMP projects out the RKB coefficients transformed to orthonormal basis and then adds the remained, corresponding to the UKB complement. With the keyword you can set the threshold for projection. The default is:

```
.PRJTHR
1.0D-5
```

## .PRINT¶

General print level. The higher the number is, the more output the user gets. Option of this type is useful for code debugging. By default set to:

```
.PRINT
0
```

## .CVALUE¶

Speed of light in a.u. Default (from CODATA18):

```
.CVALUE
137.035999167
```

## .LOGMEM¶

Write out a line in the output for each memory allocation done by DIRAC. This is mainly useful for programmers or for solving out-of-memory issues.

## .CODATA¶

Select the fundamental physical constants used througout the code. The values are taken from different CODATA sets. Current available data sets are CODATA86, CODATA98, CODATA02, CODATA06, CODATA10, CODATA14 and CODATA18. For the weak mixing angle and the Fermi coupling constant, there are also values reported in 1994 by the Particle Data Group (PDG) that were not included in any of those CODATA sets, and can be used with the keyword PDG94. When PDG94 is used, all other constants are taken from the Default CODATA set. Default:

```
.CODATA
CODATA18
```

## .NOSET¶

Warning

documentation missing

## .SKIP2E¶

Warning

documentation missing