Calculation density of water in nanotube

Dear all,
I would like to calculate the density of water in nanotubes when the temperature of them are changed,
in order to calculation of density I used the (mass of water)/volume inside of Nanotube, but when the water convert to ice again I reach to the same density!!, 1_ how can I fix this problem?
2_ how I can calculate only the volume of water group in nanotubes?
3_ is it possible I calculated the radial density of water in nanotubes which the center of Nanotube be the origin?

Regards,

First of all, as you described you issues, they are not Lammps related
but rather physics/scientific problems. Your colleagues/supervisor are
better positionned to address them.

Dear all,
I would like to calculate the density of water in nanotubes when the
temperature of them are changed,
in order to calculation of density I used the (mass of water)/volume
inside of Nanotube, but when the water convert to ice again I reach
to the same density!!, 1_ how can I fix this problem?

Not enough information (type and succession of simulations, exact
procedure,...) to know from where you "problem" comes.

2_ how I can calculate only the volume of water group in nanotubes?

If it is "inside" the NT (e.g. no interface water/vacuum), using a
Voronoi approach might be relevant.

3_ is it possible I calculated the radial density of water in
nanotubes which the center of Nanotube be the origin?

yes. But keep in mind that a density is a volume averaged quantity. So a
minimum volume has to be considered to make it consistent.

Regards,

Regards,

i’ll add two more items to julien’s list:

  • what is the density change for a bulk water system of the same water potential? most classical water potentials are particularly bad at getting the experimental behavior around the melting point right.
  • as an indirect measure consider the following: does the number of water molecules inside the nanotube change? does the diameter of the nanotube change?

and to emphasize his last point:
unless the nanotube has a sufficient diameter, you cannot automatically expect bulk-like behavior from whatever is in there. considering the popularity of nanotubes over the last 20+ years, there must be a wealth of publications on the subject. a proper and sufficiently deep study of the published literature is thus strongly recommended. don’t expect that a post to a mailing list can serve as a sufficient replacement.

axel.