Dear all,
In my internet searching I found one spetacular Home Page
located at
http://www.caos.kun.nl/cgi-bin/csecm/csecm
you can Examine space groups, Examine structures
I strongly recommend it, It was very helpfull for me. Remember
that I asked the data for Nickel Cloride Hidrates ? Here I found all them
and saw them graphically (in Virtual Reality).
Some description of this site:
N-dimensional space groups play an important role in the description of
incommensurate crystals, like quasi crystals and incommensurately
modulated crystals. These types of materials can be looked upon as the
intersection of the physical space with a higher-dimensional lattice
periodic structure. The dimension of the latter is equal to the number of
indices needed for the diffraction pattern. The purpose of the programme
is to provide information about the space groups of arbitrary dimensions.
It allows for manipulation and inspection of the groups, e.g. Wyckoff
positions, point group symmetry and systematic extinctions. Visualization
of space groups, e.g. of the general or special positions or the space
group elements, is done using VRML (Virtual Reality Modelling Language).
The number of space groups increases rapidly when one goes to higher
dimensions. This makes it not feasible to present the information as a
printed volume. The information, generated from data (generating elements)
in a data base, or from user supplied data comprises the space groups, the
symmetry elements, the Wyckoff positions and the general and special
extinctions. The goal is to show all data present in the existing tables
for 2 and 3 dimensions, with the benefit of choosing an arbitrary origin
and setting.
The user computer interaction is realized using FORMs and POSTs sent
between a special HTTP daemon and the user's WWW browser, giving the
interactive feel of a local computer programme. The FORM interface
features buttons of all kinds, input fields, checkboxes and selection
menus.
Sincerely,
__________________________________________________________________________
Hannes Fischer - Estudante de Fisica - IFUSP - email: [EMAIL PROTECTED]
Telefone: (011) 818 7110, 818 6814
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