The vregime.in file

When the vregime.in file is present during an MD simulation, the volume of the unit cell will change as the simulation proceeds.

How fast the cell parameters change is controlled by this file which looks like:
(See ~jkua/reac/MDtemp3/vregime/ for an example.)

mes
#start #V type1 change/it rescale type 2  change/it  rescale
0000    3  a    -0.0002   y     b       -0.0002       y         c   -0.0002   y

0000 means start this process at Step 0000
3 means you have three axes to change (a,b,c)
You are changing each of these axes by -0.0002 per step and then rescaling (y for yes).

You can follow the output in fort.77, for example:

      10 7997.60   20.00   20.00   20.00   90.00   90.00   90.00
      20 7995.20   20.00   20.00   20.00   90.00   90.00   90.00
      30 7992.80   19.99   19.99   19.99   90.00   90.00   90.00
      40 7990.40   19.99   19.99   19.99   90.00   90.00   90.00
      50 7988.01   19.99   19.99   19.99   90.00   90.00   90.00
      60 7985.61   19.99   19.99   19.99   90.00   90.00   90.00
      70 7983.21   19.99   19.99   19.99   90.00   90.00   90.00
      80 7980.82   19.98   19.98   19.98   90.00   90.00   90.00
      90 7978.42   19.98   19.98   19.98   90.00   90.00   90.00
     100 7976.02   19.98   19.98   19.98   90.00   90.00   90.00
     110 7973.63   19.98   19.98   19.98   90.00   90.00   90.00
     120 7971.23   19.98   19.98   19.98   90.00   90.00   90.00
     130 7968.84   19.97   19.97   19.97   90.00   90.00   90.00
     140 7966.45   19.97   19.97   19.97   90.00   90.00   90.00
     150 7964.05   19.97   19.97   19.97   90.00   90.00   90.00
(lots more in the middle)
   19900 4111.38   16.02   16.02   16.02   90.00   90.00   90.00
   19910 4109.84   16.02   16.02   16.02   90.00   90.00   90.00
   19920 4108.30   16.02   16.02   16.02   90.00   90.00   90.00
   19930 4106.76   16.01   16.01   16.01   90.00   90.00   90.00
   19940 4105.22   16.01   16.01   16.01   90.00   90.00   90.00
   19950 4103.68   16.01   16.01   16.01   90.00   90.00   90.00
   19960 4102.15   16.01   16.01   16.01   90.00   90.00   90.00
   19970 4100.61   16.01   16.01   16.01   90.00   90.00   90.00
   19980 4099.07   16.00   16.00   16.00   90.00   90.00   90.00
   19990 4097.54   16.00   16.00   16.00   90.00   90.00   90.00
   20000 4096.00   16.00   16.00   16.00   90.00   90.00   90.00

The first column is the step you're on, the second column is the volume of the system, the third through fifth columns are the lengths of the a,b,c axes, the last three columns are the angles (90 degrees for a cubic cell).

The example above was a compression from a 20x20x20 cube down to 16x16x16 over 20000 steps. You run this job similar to an MD simulation. Don't forget to specify the appropriate MD simulation parameters too.