STEER

NAME
STEER - Provide the starting and final time (in fs) for a steered molecular dynamics. The time dependent harmonic potential is defined in the namelist &POTENTIAL using the command ADD_STR_BONDS, ADD_STR_BENDS, ADD_STR_TORS.

SYNOPSIS
STEER     tiniz    tfinal
STEER     temperature  temp0    tempt   tiniz   tfinal

DESCRIPTION
Steer the system with the time dependent mechanical potential defined in the namelist &POTENTIAL, starting the SMD at time tiniz and ending at time tfinal. This command can also be used to gradually change the temperature in conjunction with the command PLOT STEER_TEMPERATURE(&INOUT) where the adimensional thermal work done on the thermostat is printed at regular time intervals (see the PLOT (&INOUT) command). Steered molecular dynamics can be automatically restarted. In order to do this, one sets once for all the steering time ( ${\it tfinal}$) to the desired value, updating, at each restart, only the simulation time given by the TIME(&RUN) directive.

EXAMPLES

 
&RUN
 ...
 STEER 1000.0 10000.0
 ..
&END
&INOUT 
 ..
 PLOT STEER_ANALYTIC  100.0  OPEN WRK.out
 ..
&END

Start to apply the time dependent potential (see Eq. 8.13) at 1 ps and switch it off at 11 ps. Print out the accumulated work every 100 fs to the file WRK.out. The accumulated work is calculated according to Eq. 8.16.

 
&RUN
 ...
 STEER temperature 300. 1500. 1000.0 11000.0
 ..
&END
&INOUT 
 ..
 PLOT STEER_TEMPERATURE  100.0  OPEN WRKTEMP.out
 ..
&END

rise the temperature form 300 to 1500 K starting at 1 ps and ending at 11 ps, with the constant speed of 120 K /ps. The thermal work is printed every 100 fs to the file WRKTEMP.out.

 
&RUN
 CONTROL 1
 STEER  0.0 18000.0
 TIME 10000.0
 ..
&END
&INOUT 
 ..
 PLOT STEER_ANALYTIC  100.0  OPEN WRK.out
 ..
&END 
.. 
&INOUT                               
   RESTART                           
       read file.rst                
       write  30.0 OPEN new.rst  
   END
&END

In this example, the simulation starts from the restart file file.rst and goes from the time found in that file to 10000.0 fs. The total steering time is 18000.0 fs. In the next restarted run the configuration of the system at $t=10000$ fs is found in the file new.rst. The next restarted simulation could be thus of the kind:

 
&RUN
 CONTROL 1
 STEER  0.0 18000.0
 TIME 18000.0
 ..
&END
&INOUT 
 ..
 PLOT STEER_ANALYTIC  100.0  OPEN WRK_10000_18000.out
 ..
&END 
.. 
&INOUT                               
   RESTART                           
       read new.rst                
   END
&END

In this example, the steering is complete and in the output file WRK_10000_18000.out, the work is calculated from $t=10000$ fs to $t=18000$ fs.