Reaction_Path has a procedure for generating a steepest-descent reaction path.
The use of this module fully explained in chapter 6 of the book A Practical Introduction to the Simulation of Molecular Systems.
Module | Variables |
---|---|
DEFINITIONS | DP |
IO_UNITS | OUTPUT |
STATUS | ERROR |
DIAGONALIZATION | SYMMETRIC_UPPER |
ATOMS | ATMCRD, ATMFIX, NATOMS, NFIXED, NFREE |
DCD_IO | Many of the public items in the module. |
NORMAL_MODE_UTILITIES | Most of the public items in the module. |
POTENTIAL_ENERGY | ATMDER, ATMHES, ETOTAL, GRADIENT, HESSIAN |
None.
There is a single public subroutine in this module.
Subroutine | Purpose |
---|---|
REACTION_PATH_TRACE | Generate a steepest-descent reaction path. |
Argument | Type | Intent | Optional | Purpose |
---|---|---|---|---|
DIRECTION | Character ( Len = 1 ) | In | No | The direction in which to trace the path. |
MAXSTP | Integer | In | No | The number of steps to take in tracing the path. |
PRINT_FREQUENCY | Integer | In | Yes | The print frequency. |
FROM_SADDLE | Logical | In | Yes | A flag to indicate the starting structure for the path tracing is a saddle point. |
USE_MASS_WEIGHTING | Logical | In | Yes | The mass-weighting flag. |
ENERGY_STEP | Real | In | Yes | The estimated energy decrease when taking the first step of a path away from a saddle point. |
PATH_STEP | Real | In | Yes | The path-tracing step size. |
SAVE_FREEQUENCY | Integer | In | Yes | The frequency for saving structures on a trajectory file. |
FILE | Character ( Len = * ) | In | Yes | The trajectory file name. |
Error | Meaning |
---|---|
Unknown direction. | The argument DIRECTION is neither "+" nor "-". |
Path file name absent. | The trajectory file name is missing. |
The starting structure is not a saddle point. | The starting structure does not have the correct curvature. |
The algorithm used could be greatly improved. Otherwise, stable.