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                 Self-Guided Langevin Dynamics (SGLD) simulation

                      By Xiongwu Wu and Bernard R. Brooks


     The SGLD simulation is a Langevin Dynamics simulation with
enhanced systematic motion.  A guiding force which is a local average
of friction forces is calculated during the simulation and used to
enhance slow motions.  Two guiding parameters, local average time and
guiding factors, are used to define the guiding effect as well as the
friction constant is used to define Langevin dynamics.  This method is
implemented in DYNAMC command and can be activated by a "SGLD" key
word.  Friction constants need be defined before DYNAMC command.

* Menu:

* Syntax::              Syntax of the SGLD dynamics command
* Examples::            SGLD usage examples

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[Syntax SGLD]

DYNAMC LANG SGLD TSGAVG real SGFT real [SGMV] other-dynamc-spec


Keyword  Default  Purpose

SGLD     false    Turn on SGLD simulation

TSGAVG   0.1 ps   Local average time

SGFT     0.5      Guiding factor

SGMV     false    Allow guiding force on the center of mass

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                        Examples

1) SGLD simulation with a friction constant of 1.

! Set friction forces
SCAL FBETA SET 1.0 SELE ALL END

! Perform SGLD simulation
DYNA LANG LEAP  STRT  NSTE 1000000 TIME 0.002  -
   IPRFRQ 10000 ISVFRQ 1000 IHTFRQ 0 IEQFRQ 0 INBFRQ 10 IHBFRQ 0 -
   IUNREA -1 IUNWRI 31 IUNCRD 32 IUNVEL 33 KUNIT -1 -
   NSAVC 1000 NSAVV 00 NPRINT 1000 ISEED 314159 -
   SGLD  TSGAVG 0.1 SGFT 1.0 -
   TBATH 300   FIRST 260 -
   IASORS 0 IASVEL 1 ICHECW 0 -
   NBXMOD 5  ATOM RDIEL SHIFT VATOM VDISTANCE VSWIT -
   CUTNB 14.0  CTOFNB 13.0  CTONNB 10.0  EPS 1.0  E14FAC 1.0  WMIN 1.0

2) SGLD simulation with a particle in external potential surface.
Guiding force on the center of mass is needed.

! Set friction forces
SCAL FBETA SET 1.0 SELE ALL END

! Perform SGLD simulation
DYNA LANG LEAP  STRT  NSTE 1000000 TIME 0.002  -
   IPRFRQ 10000 ISVFRQ 1000 IHTFRQ 0 IEQFRQ 0 INBFRQ 10 IHBFRQ 0 -
   IUNREA -1 IUNWRI 31 IUNCRD 32 IUNVEL 33 KUNIT -1 -
   NSAVC 1000 NSAVV 00 NPRINT 1000 ISEED 314159 -
! Specify SGMV to allow guiding force on the center of mass
   SGLD  TSGAVG 0.1 SGFT 1.0 SGMV -
   TBATH 300   FIRST 260 -
   IASORS 0 IASVEL 1 ICHECW 0 -
   NBXMOD 5  ATOM RDIEL SHIFT VATOM VDISTANCE VSWIT -
   CUTNB 14.0  CTOFNB 13.0  CTONNB 10.0  EPS 1.0  E14FAC 1.0  WMIN 1.0