13.11 The Explicit Polarization (XPol) Method

13.11.4 Examples

XPol on its own is not a useful method because it neglects all intermolecular interactions except for polarization, so the two examples below demonstrate the use of XPol in conjunction with a Lennard-Jones and a Buckingham potential, respectively.

Example 13.24  An XPol single point calculation on the water dimer using a Lennard-Jones potential. Löwdin atomic embedding charges (which is the default) are used.

$molecule
0 1
-- water 1
0 1
O          -1.364553     .041159     .045709
H          -1.822645     .429753    -.713256
H          -1.841519    -.786474     .202107
-- water 2
0 1
O           1.540999     .024567     .107209
H            .566343     .040845     .096235
H           1.761811    -.542709    -.641786
$end

$rem
   METHOD           HF
   BASIS            3-21G
   XPOL             TRUE
$end

$xpol_mm
   1 O          -1.364553     .041159     .045709 1 2 3
   2 H          -1.822645     .429753    -.713256 2 1
   3 H          -1.841519    -.786474     .202107 2 1
   4 O           1.540999     .024567     .107209 1 5 6
   5 H            .566343     .040845     .096235 2 4
   6 H           1.761811    -.542709    -.641786 2 4
$end

$xpol_params
   1            0.16     3.16
   2            0.00     0.00
$end

Example 13.25  An XPol single point calculation on the water dimer using a Buckingham potential.

$molecule
0 1
-- water 1
0 1
O          -1.364553     .041159     .045709
H          -1.822645     .429753    -.713256
H          -1.841519    -.786474     .202107
-- water 2
0 1
O           1.540999     .024567     .107209
H            .566343     .040845     .096235
H           1.761811    -.542709    -.641786
$end

$rem
   METHOD           HF
   BASIS            3-21G
   XPOL             TRUE
$end

$xpol_mm
   1 O          -1.364553     .041159     .045709 1 2 3
   2 H          -1.822645     .429753    -.713256 2 1
   3 H          -1.841519    -.786474     .202107 2 1
   4 O           1.540999     .024567     .107209 1 5 6
   5 H            .566343     .040845     .096235 2 4
   6 H           1.761811    -.542709    -.641786 2 4
$end

$xpol_params
   BUCKINGHAM   500000.0 12.5 2.25
   1            0.16     3.16
   2            0.00     0.00
$end