.. _hyperdynamics:
=============
Hyperdynamics
=============
The hyperdynamics method uses a bias potential which should be zero at
transition states and positive in minima in order to accelerate the rate of
transitions. [#voter97_3908]_ The hyperdynamics time step :math:`\delta t`
can be obtained from the molecular dynamics simulation time step :math:`\delta
t^b` multiplied by a boost factor :math:`e^{\beta \Delta V}`, where
:math:`{\Delta V}` is the bias potential.
There are several possible forms of bias potential. In EON, we have implemented
the bond-boost method, [#miron03_6210]_ where the bias potential is controlled
by the maximal (fractional) change in any bond length in the system. This is a
good bias potential for systems in which the dynamics is governed by bond
breaking and forming events.
You can run a hyperdynamics job by setting the **bias_potential** option.
It should be run with the ``parallel_replica`` job.
[Hyperdynamics] Options
=======================
**bias_potential**:
default: ``none``
options:
``bond_boost``: bond boost method
``none``: with no bias potential, run regular MD
**bb_dvmax**:
default: ``0.0``
The magnitude of the bond-boost bias potential.
**bb_rmd_time**:
default: ``100.0``
Regular MD duration used to determine the equilibrium bond length before the bias potential is added.
**bb_rcut**:
default: ``3.0``
All bonds which belong to the tagged atoms and are shorter than a cutoff of rcut will be included in the bond-boost potential.
**bb_stretch_threshold**:
default: ``0.2``
Defines the bond-boost dividing surface. It should be smaller than the
maximum fractional nearest-neighbor bond stretch or compression at any
transition state.
**bb_ds_curvature**:
default: ``0.95``
The curvature near the bond-boost dividing surface, it should has a value
<= 1. We recommend the value to be 0.9-0.98.
.. rubric:: References
.. [#voter97_3908] A.F. Voter "Hyperdynamics: Accelerated Molecular Dynamics of Infrequent Events" *Phys. Rev. Lett.* **78**, 3908 (1997)
.. [#miron03_6210] R.A. Miron and K.A. Fichthorn "Accelerated molecular-dynamics of rare events with the bond-boost method" *J. Chem. Phys.* **119**, 6210 (2003)