.gro文件中坐标与坐标之间隔多少个字符是不是要特别注意。我在http://manual.gromacs.org/online/gro.html站中看了一段话，不是很明白其中的意思。This format is fixed, ie. all columns are in a fixed position. Optionally (for now only yet with trjconv) you can write gro files with any number of decimal places, the format will then be n+5 positions with n decimal places (n+1 for velocities) in stead of 8 with 3 (with 4 for velocities). Upon reading, the precision will be inferred from the distance between the decimal points (which will be n+5). Columns contain the following information (from left to right):
residue number (5 positions, integer)
residue name (5 characters)
atom name (5 characters)
atom number (5 positions, integer)
position (in nm, x y z in 3 columns, each 8 positions with 3 decimal places)
velocity (in nm/ps (or km/s), x y z in 3 columns, each 8 positions with 4 decimal places)