[gmx-users] question about g_hydorder

[Nidhi Katyal]

Dear all
I would like to calculate angle tetrahedral order parameter of water
molecules as defined by  Chau et al (eq 3). I am using g_hydorder of
gromacs 4.6.3 with my index group containing all oxygen atoms of water:
g_hydorder -f *.xtc -s *.tpr -o file1.xpm file2.xpm -or file_1.out
file_2.out -n index.ndx
I am getting following error;
No or not correct number (2) of output files :1
It seems from above that correct number should be 2 but user is supplying
only 1 and so is the error. But I am giving names of two output files.
Also, I am unable to understand what exactly is contained in these two/four
output files. I tried to comprehend this by looking at gmx_hydorder.c and
could make a guess that I actually need sgmol/sgmean (variables as defined
in program) as the final output.
Please help me understand the usage of this command in order to fulfill my
aim.Thanks in advance.