Pathways are calculated by starting a minimisation of some sort after stepping off the
transition state specified in odata.
Using MODE values of 1 and will give the two sides of the path.
With SEARCH 0 (or 3) or LBFGS minimisation
the resulting pathway will only be an approximation to a true
gradient line. For search type 6 (or 7) and RKMIN or BSMIN
the results should be close to the true steepest-descent
path. Note that gradient lines are properties of the potential energy surface alone, and
do not depend upon masses. Mass weighting, or calculating pathways in the fictitious
space with a kinetic metric,[80] has now been implemented, but not in the BFGS
minimisation or hybrid EF/BFGS routines.
From svn revision 24173 it is possible to follow a transition state search by a pathway calculation automatically. The transition state search can be specified by BFGSTS, including NOIT and NOHESS, or full eigenvector-following using SEARCH 2. The default minimisation uses eigenvector-following if no other method is specfied. Otherwise the paths can be calculated by specifying BFGSMIN, PMPATH, BBRSDM, RKMIN, or BSMIN. Example input and output can be found at http://www-wales.ch.cam.ac.uk/examples/OPTIM/. The following input is for a gradient-only hybrid eigenvector-following transition state search with pathways calculated using LBFGS energy minimisation:
MAXBFGS | 0.2 0.2 |
DUMPALLPATHS | |
PATH | 1000 0.0 |
MAXSTEP | 0.1 |
MAXMAX | 0.2 |
TRAD | 0.2 |
BFGSTS | 100 3 25 0.001 |
UPDATES | 10 10 |
NOHESS | |
BFGSMIN | 1.0D-7 |
CONVERGE | 1.0D-4 1.0D-7 |
PUSHOFF | 0.02 |
STEPS | 200 |
BFGSSTEPS | 5000 |
POINTS | |
etc. |
The DUPALLPATHS keyword results in a path.info file being created, which can be read into a discrete path sampling database for PATHSAMPLE using the ADDPATH keyword for that program.
David Wales 2015-11-16