A geometry optimization library for quantum chemical and QM/MM calculations to
be included into electronic structure codes.
DL-FIND can be used to search for minima, transition states (the main
strength of the code), and conical intersections.
All work totally or partially based on DL-FIND should cite
 as well as the original references
of the optimization algorithms used (references given in
A light-weighted description of geometry optimization in general and DL-FIND in
particular can be found in Frontiers 2007.
- Cartesian coordinates (including frozen atoms and components),
mass-weighted Cartesian coordinates
- Internal coordinates (including all constraints):
- DLC (delocalized internal coordinates, i.e. redundant internal coordinates)
- DLC-TC (total connection)
- HDLC (hybrid delocalized internal coordinates, see Phys. Chem. Chem. Phys. 2, 2177 (2000))
Combinations of coordinates (images):
All of the combinations work with all versions of coordinate systems.
- Dimer method 
- NEB (nudged elastic band) 
- steepest descent
- conjugate gradient
- P-RFO, Hessian update mechanisms: Powell and Bofill. Hessian
either by input or by finite-difference. In the latter case either in
Cartesians (then the update also in Cartesians, and one can output
frequencies), or in internals.
- Damped dynamics
- Algorithms for Conical intersection search:
- Penalty function
- Gradient projection method
- Lagrange-Newton method
- Stochastic search methods (including a genetic algorithm) for global and
local minimization. These methods optimize by calculating may energies in
parallel and are thus well-suited for massively parallel computation.
Line search algorithms:
The design allows new methods to be easily implemented.
- Simple scaling of the proposed step (covering the maximum step length)
- Trust radius based on energy decrease
- Trust radius based on the projection of the gradient on the step
Reaction rate calculations with or without tunneling contributions
- Instanton theory (aka imaginary-F theory or harmonic quantum
transition state theory) to calculate tunneling rates.
- Instanton optimizations with a quadratically-converging optimizer 
- Instanton rate calculations (parallelized)
- Adaptive step size in instanton calculations
- Reaction rates without tunneling
- The optimizer is fully restartable.
- DL-FIND can be included in ChemShell
and was used in conjuction with a nuber of other codes
- Johannes Kästner, main author
- Tom W. Keal contributed conical intersection search algorithms,
parallelization of NEB and finite-difference Hessian calculations
and fixed many bugs.
- Joanne M. Carr is adding parallel search algorithms
- Judith B. Rommel contributed to the implementation of instanton theory
- Salomon Billeter and Alexander Turner: parts of their HDLCopt routines have been used in
the coordinate transformation, by courtesy of the Max-Planck-Institute for coal
- The L-BFGS
code by Jorge Nocedal was used
DL-FIND is distributed at http://ccpforge.cse.rl.ac.uk/projects/dl-find/
under the L-GPL license. It can be checked out (svn) after registering at CCPForge.
It is written in Fortran 95. The interface to the calling program is kept slim
and well-defined, which should facilitate to interface DL-FIND to various
programs. Up to now, DL-FIND is included in ChemShell, GAMESS-UK,
TeraChem, and a few other codes.
Trajectories of two transition-state searches using the dimer method in
DL-FIND. The dimer midpoint converges to the transition state (blue
The dimer method applied to a biological system (the enzyme PHBH) in HDLC
Converged nudged-elastic band path on an example surface
(Müller-Brown potential). The green spheres indicate minima, the blue
sphere indicates the climbing image which converged to the transition state.
Energy and geometries of a nudged-elastic band path of a simple chemical
system, optimized with DL-FIND.