Next: Dynamics Up: Standard Minimization and Dynamics Previous: Boundary Conditions   Contents   Index

Subsections

## Energy Minimization

The default minimizer uses a sophisticated conjugate gradient and line search algorithm with much better performance than the older velocity quenching method. The method of conjugate gradients is used to select successive search directions (starting with the initial gradient) which eliminate repeated minimization along the same directions. Along each direction, a minimum is first bracketed (rigorously bounded) and then converged upon by either a golden section search, or, when possible, a quadratically convergent method using gradient information.

For most systems, it just works.

• minimization Perform conjugate gradient energy minimization?
Acceptable Values: on or off
Default Value: off
Description: Turns efficient energy minimization on or off.

• minTinyStep first initial step for line minimizer
Acceptable Values: positive decimal
Default Value: 1.0e-6
Description: If your minimization is immediately unstable, make this smaller.

• minBabyStep max initial step for line minimizer
Acceptable Values: positive decimal
Default Value: 1.0e-2
Description: If your minimization becomes unstable later, make this smaller.

• minLineGoal gradient reduction factor for line minimizer
Acceptable Values: positive decimal
Default Value: 1.0e-4
Description: Varying this might improve conjugate gradient performance.

### Velocity quenching parameters

You can perform energy minimization using a simple quenching scheme. While this algorithm is not the most rapidly convergent, it is sufficient for most applications. There are only two parameters for minimization: one to activate minimization and another to specify the maximum movement of any atom.

• velocityQuenching Perform old-style energy minimization?
Acceptable Values: on or off
Default Value: off
Description: Turns slow energy minimization on or off.

• maximumMove maximum distance an atom can move during each step (Å)
Acceptable Values: positive decimal
Default Value: cutoffstepsPerCycle
Description: Maximum distance that an atom can move during any single timestep of minimization. This is to insure that atoms do not go flying off into space during the first few timesteps when the largest energy conflicts are resolved.

Next: Dynamics Up: Standard Minimization and Dynamics Previous: Boundary Conditions   Contents   Index
http://www.ks.uiuc.edu/Research/namd/