Electronic and Molecular Structure of a Water Molecule neat a Brucite Surface
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The files bru+h2o.shak and bru+h2o.fld represent the nuclear
co-ordinates and valence electron density of a water molecule bonded
to a brucite (Magnesium Hydroxide) surface.  The co-ordinates and
electron density were calculated using density functional/
pseudopotential methods using the local density approximation and
plane-wave basis sets.   The program CASTEP was used to perform the
calculations.

The networks use the READ SHAK module (available from the IAC) to generate
a ball-and-stick representation of the molecule and surface and various
volumetric rendering techniques to visualize the electron density.

The field file bru+h2o-orig.fld demonstrates how to read in the data
using the data-parsing mode of "read field" and how to match the field
to the geometry by setting the points and extents elements of the
field.  The file bruh2o.coord contains the points information.
(read_field won't accept filenames containing a '+'.)

The colour-code for the ball-and-stick atoms is
	Hydrogen	light blue
	Oxygen		Red
	Magnesium	Grey

The distortion of the brucite lattice caused by the water molecule can
be clearly seen as can the electron "brigde" between the hydrogen of
the layer and the oxygen of the water molecule.  This is a hydrogen
bond.  Note also the almost complete absence of electon density around
the Mg ions and its transfer to the OH groups.  This demonstrates that
brucite is a highly ionic material.