[gmx-users] H-bonds in water + alcohol mixture

[Nuno Garrido]

Dear all,

I'm trying to evaluate the number of H-bonds in a 150 alcohol (TraPPE)
+ 57 water (SPC/E) molecules mixture.

>From rdf analysis I can observe that the most prominent peak is
related to OW-OW group, followed by OW-OH group and finally OH-OH
group.
OW = water oxygen
OH = alcohol oxygen.

>From g_hbond analysis I have calculated (at fixed cutoff = 0.35 nm +
angle = 30º) the following average number of hydrogen bonds per time
step:
Water - Water     = 36.53 --> 36.53 / 57    = 0.64 per molecule
Water - Alcohol   = 106.13 --> 106.13/207 = 0.513
Alcohol - Alcohol = 96.23 --> 96.23/150    = 0.64

I was expected to observe the same trend in both rdf and number of
H-bonds... Someone has some clue about what I am doing wrong ?

Thanks in advance
Nuno Garrido