# Talk:Water model

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## Models

One-site models also exist for water. A comprehensive discussion of water models is incomplete without a brief discussion of them. Momolee 11:56, 25 May 2007 (UTC)

I don't know much about such models, but please feel free to add more information and references. For now, I've deleted the blank 1-site section as it serves no purpose. --Itub 14:29, 4 June 2007 (UTC)

## unit problem in equation

The equation dimensions doesn't make sense,since you are adding C/Å + cal/mol, what unit do you get? Thus constant e should be replaced(?) by Faraday Constant C/mol. Any how I'm working with water now, and I'll be back with more information. GA Fantastic (talk) 10:07, 21 January 2008 (UTC)

The equation is taken straight from the 1983 reference. However, it is true that it's missing a conversion factor, the electrostatic constant, which depends on the system of units used. Normally the programs implementing water models have it hard-coded (including the e^2 constant) such that (k q_1 q_2)/r gives the energy in kcal/mol when r in in angstrom and q_i in electron charges. --Itub (talk) 12:07, 21 January 2008 (UTC)
I think this should by clarified on the page, because of possible confusion.Since constans A and B are defined as cal/mol the conversion constant should by set k=332.1. I can't find proper references for the calculations of the constant. More ever I think it would by nice to include table of top (H2O)n cluster, which can by found at http://www-wales.ch.cam.ac.uk/~wales/CCD/TIP4P-water.html as well the geometries of well know clusters. GA Fantastic (talk) 14:17, 21 January 2008 (UTC)
I checked and I agree that the conversion factor is 332.1. I'll add that to the article. Regarding the clusters, perhaps a more appropriate place is at the water cluster article, but at least I'll add a mention that water models are also used for clusters and not only for bulk liquids! --Itub (talk) 17:43, 21 January 2008 (UTC)