# [gmx-users] Have read the manual => How to calculate dihedral angle??????

Chih-Ying Lin chihying2008 at gmail.com
Wed Jul 2 07:42:11 CEST 2008

```HI
I have read the manual  but the thing is that I could not get the
answers from the manuals.  So, I repeatly ask the same questions and
if anyone could give me the exact answers. Thanks a lot.

Lin

I use   mk_angndx   to     produce      angle.ndx
then, enter  g_angle -od angdist.xvg -ov angaver.xvg -type dihedral

it follows the options:
Group     0 (Phi=180.0_2_70) has     4 elements
Group     1 (Phi=180.0_2_6) has    16 elements
Group     2 (Phi=180.0_2_40) has   192 elements
Select a group:

what does the file angle.ndx mean?
what are the three groups represent ?
which group should I pick up?

this is the angle.ndx
what does it mean??
[ Phi=180.0_2_70 ]
11    12    13    14
[ Phi=180.0_2_6 ]
7    11    12    13     9    11    12    13    12    13    14    15
12    13    14    17
[ Phi=180.0_2_40 ]
2     1     3     4     2     1     3     7     5     1     3     4
5     1     3     7     4     3     7     8     1     3     7     8
1     3     7    11     4     3     7    11     8     7    11    12
3     7    11     9     8     7    11     9     3     7    11    12
7    11     9     5     7    11     9    10    12    11     9     5
12    11     9    10    11     9     5     1    11     9     5     6
10     9     5     1    10     9     5     6     9     5     1     3
9     5     1     2     6     5     1     3     6     5     1     2
13    14    15    16    13    14    15    19    17    14    15    16
17    14    15    19    14    15    19    23    14    15    19    20
16    15    19    23    16    15    19    20    15    19    23    21
15    19    23    24    20    19    23    21    20    19    23    24
19    23    21    17    19    23    21    22    24    23    21    17
24    23    21    22    23    21    17    14    23    21    17    18
22    21    17    14    22    21    17    18    21    17    14    15
21    17    14    13    18    17    14    15    18    17    14    13

Thanks

Lin

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