To carry out a PE-SCF calculation with the DSCF or RIDFT module, you have to specify the following in the `control` file:

$point_charges pe [options] <length unit> <no. MM sites> <order k> <order pol> <length exclude list> <list of MM sites: exclude list, xyz coords, multipole mom., pol. tensor>

**length unit**- specifies the unit for the MM site coordinates (use
`AA`or`AU`) **no. MM sites**- the amount of MM sites (length of the list)
**order k**- the order of multipoles used (0: point charges, 1: dipole moments, 2: quadrupole moments, 3: octupole moments)
**order pol**- the treatment of polarizabilities (0: none, 1: isotropic, 2: anisotropic)
**length exclude list**- number of elements in the exclude list
**list of MM sites**- each MM sites is described on one line, entries separated by blanks; first entry is the exclude list of with as much elements as defined in the head line (If the first element in the exclusion list of one site occurs in the exclude list of another site, they do not contribute to each others polarization); next follows the MM site coordinates in (x,y,z positions), the point charge, the dipole moment (for
, x,y,z component), the quadrupole moment (for*k*≥1, xx, xy, xz, yy, yz, zz component), the octupole moment (for*k*≥2, xxx, xxy, xxz, xyy, xyz, xzz, yyy, yyz, yzz, zzz component), the polarizability ( one component for pol-order 1, xx, xy, xz, yy, yz, zz component for pol-order 2)*k*= 3

An example for a polarizable embedding with coordinates given in Å, point charges and isotropic polarizabilities:

$point_charges pe AA 6 0 1 1 39 -0.2765102481 2.5745845304 3.5776314866 0.038060 15.217717 39 1.3215071687 2.3519378014 2.8130403183 -0.009525 14.094642 39 -0.5595582934 1.2645007691 4.7571719292 -0.009509 14.096775 39 -1.5471918244 2.5316479230 2.3240961995 -0.009519 14.096312 39 -0.3207417883 4.1501938400 4.4162313889 -0.009507 14.096476 41 -1.1080691595 4.9228723099 -1.6753825535 0.038060 15.217717 41 -0.9775910525 6.5274614891 -2.4474576239 -0.009525 14.094642 41 -2.5360480539 4.8923046027 -0.6040781123 -0.009509 14.096775 41 0.3630448878 4.6028736791 -0.7155647205 -0.009519 14.096312 41 -1.2817317422 3.6689143712 -2.9344225518 -0.009507 14.096476

All values are given in atomic units (except coordinates if stated otherwise). These data are mandatory. In addition, you can specify further options on the same line as the `$point_charges` flag. These are:

`rmin=<float>`: minimum distance between an active MM site and any QM center (in a.u.), treatment is handle by option`iskip`, (DEFAULT: 0.00 a.u.)`iskip=(1,2)`: treatment of too close MM sites- (1) zeroing all contributions
- (2) distribute values to nearest non-skipped MM site (DEFAULT)

`rmax=<float>`: maximum distance between an active MM site and QM center of coordinates (in a.u.), sites too far away are skipped (zeroed) (DEFAULT: 1000.00 a.u.)`nomb`: no treatment of many body effects between induced dipoles (all interaction tensors on the off-diagonal of the response matrix are set to Zero); works best with isotropic polarizabilities, speeds up calculations (especially for large response matrices), has reduced accuracy, not well tested so far`longprint=(1,2,3)`: sets a flag for additional output- (1) print all MM site input information
- (2) additionally: print all induced dipoles due to nulcei/multipole/electron electric filed
- (3) additionally: print response matrix

`file=<input file>`: specifies a file from which the data group`$point_charges`is read. Note that all options which are following on the line the`control`file are then ignored because reading continues in the input file (But here, further options can be specified after the`$point_charges`flag). The file has to start with`$point_charges`as top line and should be finished with`$end`

Limitations with respect to standard SCF computations:

- In PE-SCF computations, symmetry cannot be exploited.
- PE-SCF computations do not work in parallel (MPI parallelization).

The energy of a PE-SCF calculation printed in the output contains the following terms:

EPE-SCF = EQM + EQM/MM, es + Epol |
(9.29) |

Here,
** EQM**
is the energy of the quantum mechanical method of your choice,

At the moment, TURBOMOLE does not offer the possibility to generate the necessary potentials or to create a potential file from a set of coordinates. Embedding potentials can be obtained from literature or generated by approaches like the LoProp method.[122] Atom centered polarizabilities are also available from other methods or from experiment. Finally, there are some polarizable force fields which, in principle, can be used for the PE method (for example, the AMOEBA force field).