From: hal@finney.org
Date: Mon Oct 11 1999 - 18:32:07 MDT
Aspiring nanotechers and nanotechesses may want to look at the current
Scientific American Amateur Scientist column, available online at
http://www.sciam.com/1999/1099issue/1099amsci.html. If you follow the
links at the bottom you can download a special demo version of a pretty
nifty-sounding molecular modelling program from Stark Designs. Here is
an excerpt from the article:
But Molecular Dynamics takes this all to a new level. It allows you to
conduct an impressive array of virtual experiments to see how different
atoms interact under all kinds of conditions. The program consists
of numerous modules that demonstrate diffusion, osmotic pressure, the
relation between temperature and pressure, the distribution of molecular
speeds in a gas and many other topics. And you can use the software to
discover things that even the most mathematically gifted physicist would
be hard-pressed to wrestle from the basic theory.
The simulation runs so fast that when I first saw it at a conference
I was certain it was a trick. The presenter put about 50 each of four
different kinds of electrically neutral atoms inside a three-dimensional
volume. The particle positions updated so quickly that I thought it
had to be a computer movie, not a real-time simulation. So I decided to
challenge the fellow.
In nature even neutral atoms can bond together. The mutual repulsion of
the orbital electrons polarizes the atoms, and it turns out there is a
range of distances over which these polarized atoms are attracted. So
I asked the presenter to add these electrostatic interactions and
then slowly decrease the temperature. He did. The heavier atoms began
clumping together while the lighter ones kept speeding about, just as
they should. He then rapidly brought the temperature to zero. The free
atoms settled into small isolated clumps, again just as they should. That
made me a believer.
I just downloaded the software but haven't tried it yet. It apparently
has a number of "modules" that run specific simulations. I don't think
you can create arbitrary scenarios with the demo software (no Drexlerian
nanosynthesis modules yet probably). But it sounds like it might be fun.
Hal
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