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Sci.chem FAQ - Part 5 of 7
Section - 21. Molecular and Structural Modelling

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Top Document: Sci.chem FAQ - Part 5 of 7
Previous Document: 20. Optical properties of chemicals
Next Document: 22. Spectroscopic Techniques
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Supplied by: Dave Young (young@slater.cem.msu.edu)

21.1  What hardware do I need to run modelling programs? 

	There are two types of programs that are referred to as molecular
modeling programs.  This first is a program which graphically displays
molecular structures as Lewis structures, ball & stick, etc.  The second
is a program which does a calculation to tell you something about the
molecule, such as it's energy, dipole moment, spectra, etc.

	For an introductory description of various types of computations,
see http://www.cem.msu.edu/~young/topics/contents.html

	There are many programs of both sorts available for a large range 
of machines.  The speed, memory, graphics and disk space on the machine 
will determine the size of molecules that can be modelled, how accurate
the model is, and how good the images will look.  There are a few programs 
that will run on a 286 PC with Windows.  There are some fairly nice things 
that can be done on a 386 with about 8 MB of RAM and Windows.  The 
professional computational chemists are generally using work stations and 
larger machines.

	Currently many computational chemists are using machines made by
Silicon Graphics (SGI) ranging from the $5,000 Indy to the $1,000,000
power challenge machines.  These are all running Irix, which is SGI's
adaptation of Unix.  SGI is popular for two reasons; first that the power
is very good for the price, second that SGIs run the largest range
of chemical software.  However, you will find some computational chemistry 
software that can run on almost any machine.

	As far as graphics quality, the SGI Onyx (about $250,000) is about 
the top of the line.  Even if you find a machine that claims to have better 
graphics than this, chances are you won't find and chemistry software that 
can utilise it.  

	For chemical calculations there is no limit to the computing
power necessary.  There are some calculations that can only be done
on the biggest Crays or massively-parallel machines in the world.  There
are also many calculations which are too difficult for any existing
machine and will just have to wait a few years or a few centuries.

21.2  Where can I find a free modelling program?

	The single best place for public domain modelling software
is probably the anonymous FTP server at ccl.osc.edu in the directory
pub/chemistry/software.  "ccl" stands for "computational chemistry
list server" and is a list frequented mostly by professional 
computational chemistry researchers.  This machine contains their 
archives with quite a bit of information as well as software.

	For work stations and larger, the program GAMESS (General Atomic
and Molecular Electronic Structure System) can be obtained as source
code from Mike Schmidt at mike@si.fi.ameslab.gov   GAMESS is a quantum
mechanics, ab initio and semi-empirical program.  It is powerful. but
not trivial to learn how to use.

	The COLUMBUS program for work stations and larger can be obtained 
by anonymous FTP from ftp.itc.univie.ac.at   It is a HF, MCSCF and 
multi-reference CI program.  This is probably the most difficult program
to use that is in use today since it requires the user to input EVERY 
detail manually.  However, because you control everything there are some
calculations that can only be done with COLUMBUS.

	CACAO is an extended Huckel program available by anonymous FTP 
at cacao.issecc.fi.cnr.it

21.3  Where can I find structural databanks? 

21.4  Where can I find ChemDraw or ChemWindows 

For ChemDraw (Macintosh, Windows, UNIX)
     CambridgeSoft Corporation
     875 Massachusetts Avenue
     Cambridge, MA 02139
     Phone: (800) 315-7300 or (617) 491-2200
     Fax: (617) 491-7203
     Internet: info@camsci.com
     http://www.camsci.com

For ChemIntosh or ChemWindows
     SoftShell
     1600 Ute Avenue
     Grand Junction, CO 81501
     Phone: (970) 242-7502
     Fax: (970) 242-6469
     Internet: info@softshell.com
     http://www.softshell.com

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Top Document: Sci.chem FAQ - Part 5 of 7
Previous Document: 20. Optical properties of chemicals
Next Document: 22. Spectroscopic Techniques

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