[gmx-users] how to edit pdb file

[Wei, Xiupeng]

Dear GMX users,
         I have a basic question. I want to put two same box in x direction. So I need increase the number of atoms and change their x coordinates,then combine it with the original one. But the file created by Excel can't be recoganized by gromacs. Is there any method in Gromacs to handle that? I also used Matlab, but it can't read pdb file correctly. Thanks.

Best regards,
xiupeng