Hello all,
I've been having a nightmare of a time trying to get order parameters for my 
lipids.  All pre-3.3 files I have can be processed quite happily with a version 
of g_order from 3.2.1, but I can't seem to get 4.0 (or 3.3.1) to produce the 
basic order.xvg.  I've tried specifying all carbons to be calculated in a 
single group - order.xvg never gets produced.  Specifying each equivalent atom 
in a different group, as worked for 3.2.1, doesn't work either - it only asks 
for one group, and even if you specify one group to just give it one type of 
carbon, that still doesn't produce order.xvg.  I get sg-ang and sk-dist 
(although sg-ang is a long sequence of zeroes at each timepoint), so the 
program is working, just not giving out the result I want at the end.  Does 
anyone have an idea what I'm doing wrong, or alternatively have a protocol that 
they know works for them?


Technical stuff for the approach I use that I think SHOULD work (have tried 
several other variations):

Commands I run (leaflet.ndx contains atoms from one leaflet in group 0, other 
leaflet in group 1):

make_ndx -f $tpr -n leaflet -o testyleaf2 <<+
t LP2 | t LP3 | t LC | a C24 | a C25 | a C45 | a C46
1 & 2
del 0
del 0
del 0
q
+
/home/ad0303/GROMACS4/bin/g_order -s $tpr -f trjShort -o test -n testyleaf2 
-nice 0 -szonly

result:

Reading file topol1.tpr, VERSION 3.2.1 (single precision)
Reading file topol1.tpr, VERSION 3.2.1 (single precision)
Select the group that contains the atoms you want to use for the tetrahedrality 
order parameter calculation:
Group     0 (leaflet2_&_LP2_LP3_LC_C24_C25_C45_C46) has  2304 elements
There is one group in the index
Reading frame       0 time    0.000
Back Off! I just backed up sg-ang.xvg to ./#sg-ang.xvg.3#
Back Off! I just backed up sk-dist.xvg to ./#sk-dist.xvg.3#
Reading frame      60 time   45.750
gcq#151: "I Ripped the Cord Right Out Of the Phone" (Capt. Beefheart)

files output:  sg-ang.xvg, sk-dist.xvg

sg-ang.xvg (small excerpt):
0.000000 0.000000
0.750000 0.000000
1.500000 0.000000
2.250000 0.000000
3.000000 0.000000
3.750000 0.000000
4.500000 0.000000
5.250000 0.000000
6.750000 0.000000
7.500000 0.000000

sk-dist.xvg
0.000000 0.025605
0.750000 0.025660
1.500000 0.025662
2.250000 0.025649
3.000000 0.025555
3.750000 0.025473
4.500000 0.025505
5.250000 0.025541




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