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 12.37 An XPol single point calculation on the water dimer using a Lennard-Jones potential. CM5 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 12.38 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