[gmx-users] adding molecules

[Dinesh Pinisetty]

Hello,
      I want to add 20 molecules of type 'A' in a box of specified
dimensions. I tried to use genbox as follows:
  genbox -cp singleA.gro -cs A.gro -nmol 20 -box 6.32000 4.80000 2.70000 -o
boxfilledA.gro

When I check boxfilledA.gro I have more than 20 molecules i.e around 50-60
molecules. Its a huge difference. What might be the problem here. How do I
need to add only required number of 20 molecules in the box of the above
defined specified dimensions.
  Any suggestions would be greatly appreciated.
Thanking you,
Dinesh.