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Computational details: SCF calculations

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 k≥1 , x,y,z component), the quadrupole moment (for k≥2 , xx, xy, xz, yy, yz, zz component), the octupole moment (for k = 3 , 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)

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

$point_charges pe
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:

Limitations with respect to standard SCF computations:

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, EQM/MM, es the electrostatic interaction energy between the QM and the MM region, and Epol the energy gain due to the total of induced dipole moments. If necessary, missing terms can be computed without knowledge of the electron distribution.

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).

next up previous contents index
Next: Computational details: PERI-CC2 calculations Up: Polarizable embedding calculations Previous: Theory   Contents   Index