The dimer method of Henkelman and Jónsson with improvements by Heyden et al and Kästner and Sherwood for estimating the lowest eigenmode using only first derivatives. 1 2 3
The dimer separation is set in the [Main] section with the finiteDifference parameter.
opt_method: Optimization algorithm to choose the dimer rotation direction
default:
cgoptions:
sd: steepest descent, rotate along the rotational force.
cg: conjugate gradient, rotate along conjugate directions.
lbfgs: Limited memory Broyden-Fletcher-Goldfarb-Shanno Quasi-Newton optimizer.
converged_angle: The dimer is considered converged if it will be rotated fewer degrees than this angle.
default:
5.0
rotations_max: This is the maximum number of rotations allowed for the dimer for each minimum mode estimation.
default:
10
References
Henkelman and H. Jónsson, “A dimer method for finding saddle points on high dimensional potential surfaces using only first derivatives,” J. Chem. Phys. 111, 7010-7022 (1999). DOI
Heyden, A.T. Bell, and F.J. Keil, “Efficient methods for finding transition states in chemical reactions: Comparison of improved dimer method and partitioned rational function optimization method,” J. Chem. Phys. 123, 224101 (2005). DOI
Kästner and P. Sherwood, “Superlinearly converging dimer method for transition state search,” J. Chem. Phys. 128, 014106 (2008) DOI