Calculates the energy & its derivative due to a single interacting pair of atoms.
Type | Intent | Optional | Attributes | Name | ||
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real(kind=rp), | intent(in) | :: | rij_mag | Distance between two atoms |
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real(kind=rp), | intent(in) | :: | qi | Charge on atom i |
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real(kind=rp), | intent(in) | :: | qj | Charge on atom j |
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integer, | intent(in) | :: | sty | Style of vdw interaction |
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real(kind=rp), | intent(in), | dimension(:) | :: | params | Parameters for vdw interaction |
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real(kind=rp), | intent(out) | :: | enrg | Energy |
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real(kind=rp), | intent(out) | :: | frc | Derivative of the potential. This is the magnitude of force due to this potential. |
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integer, | intent(out) | :: | ierr | Error flag |