[gmx-users] Gmx gangle

[rose rahmani]

Hi,

I want to calculate angle between water molecules and ZnS surface(slab). I
mean the angular distribution function(ADF) of ALPHA and BETA. I define to
angles; Alpha= angle between OH bond of water and  surface(plane)    Beta=
angle between HOH plane and surface(plane).

I used gmax gangle for Alpha:
Gmx gangle -f traj.xtc -s topol.tpr -n index.ndx -g1 vector -g2 z -oh
Then i selected water(SOL) group

For Beta:
Gmx gangle -f traj.xtc -s topol.tpr -n index.ndx -g1 plane -g2 z -oh
And again i selected water group.

But results are little odd and histograms are two plot which are symmetric
plots.

I think sth is wrong. Should i make an index file for OH bond in the case
of ALPHA? If yes how bonds defined in gmx make_ndx? because i think it
calculated the angle between COM of water vector and surface not the OH
bond of water. As you know water has 2 OH bond. So... what should i do?

How about BETA? does it really calculate what i want?

Should i make an special index file?

If i want to calculate this property (ADF) in for example 1 nm from
surface, what should i do?

To be more clear, I refer you to fig.1 and fig.8
roja:
https://www.researchgate.net/publication/257760740_Structural_properties_of_water_around_uncharged_and_charged_carbon_nanotubes/figures

Would you please help me how can i reach these goals?

Best regards

Rose