POTENTIAL_ENERGY


Function

Potential_Energy is the module concerned with the calculation of the potential energy and its coordinate derivatives.

This module is discussed in chapters 4 and 5 of the book A Practical Introduction to the Simulation of Molecular Systems.

Dependencies

Module Variables
DEFINITIONS DP
IO_UNITS OUTPUT
STATUS ERROR
ATOMS ATMCRD, ATMFIX, NATOMS, NATOMSMM, NATOMSQM, NFIXED, NFREE
CONSTRAINT ENERGY_CONSTRAINT
ENERGY_COVALENT ENERGY_ANGLE, ENERGY_BOND, ENERGY_DIHEDRAL, ENERGY_IMPROPER
ENERGY_NON_BONDING ENERGY_NON_BONDING_CALCULATE
MOPAC_ENERGY ENERGY_MOPAC


Public Variables

There are fourteen public variables in this module.

Variable Type Purpose
EANGLE Real The MM angle energy.
EBOND Real The MM bond energy.
EDIHEDRAL Real The MM dihedral energy.
EELECT Real The MM electrostatic energy.
EIMPROPER Real The MM improper dihedral energy.
ELJ Real The MM/MM and QM/MM Lennard-Jones energy.
ECONSTRAINT Real The constraint energy.
EPI Real The path integral energy.
EQM Real The QM and QM/MM electrostatic energy.
ETOTAL Real The total potential energy.
GRMS Real The RMS gradient.
VIRIAL Real The internal virial multiplied by -3.
ATMDER Real(1:3,1:NATOMS) The first derivatives.
ATMDER Real(1:(3*NFREE*(3*NFREE+1))/2) The second derivative matrix in upper triangular packed format.


Public Procedures

There are five public subroutines in this module.

SubroutinePurpose
ENERGY Calculate the potential energy of a system.
GRADIENT Calculate the potential energy of a system and its first derivatives.
HESSIAN Calculate the potential energy of a system and its first and second derivatives.
ENERGY_INITIALIZE Initialize the POTENTIAL_ENERGY scalars and deallocate the arrays ATMDER and ATMHES.
ENERGY_PRINT Print the potential energy and its various components.


ENERGY

Argument Type Intent Optional Purpose
PRINT Logical In Yes A print flag.




GRADIENT

Argument Type Intent Optional Purpose
PRINT Logical In Yes A print flag.




HESSIAN

Argument Type Intent Optional Purpose
PRINT Logical In Yes A print flag.




ENERGY_INITIALIZE

This subroutine has no arguments.



ENERGY_PRINT

This subroutine has no arguments.



Stability

Stable.



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