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Oscar Tutorial 4
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Tutorial 4:
LennardJonesium
The Search for the Global Energy Minimum
in Two and Three Dimensions
You may work alone or in a group of 23 people. Every student will try various
methods of optimizing the structure of LennardJonesium. You will prepare two
reports, one for the twodimensional case and one for the threedimensional case.
You may try any of the following algorithms:
Energy minimization
Molecular dynamics (MD) at constant temperature
Monte Carlo (MC) at constant temperature
Simulated annealing with MD
Simulated annealing with MC
You may choose any temperature protocol, by which I mean that you may use any
constant temperature, or you may use any thermalization protocol you like.
Note that, when you are running molecular dynamics, you may use any of the
various algorithms for setting and maintaining temperature.
Rule 1:
All MD and MC simulations should be run for 10,000 steps or more. You
can, of course, make test runs with fewer steps. Use whatever output frequency
gets you the information you need.
Rule 2:
All final structures should be minimized to convergence, with a
convergence criterion of 10
15
, so we will all be comparing structures at similar
stages of refinement. (Be sure you understand what “convergence” means!)
Two Dimensions:
The goal of this exercise is to determine the optimum method for finding the global
minimum. To do this, you must answer two questions:
Question 1
:
How hard is it to find the global minimum starting from an
arbitrary structure, using the algorithm (or algorithms) and the various protocols
you tested?
Question 2
:
For your algorithm of choice, what was the best protocol you
found?
The goal is
not
to obtain the lowest energy structure, because we already know
what that configuration is.
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View Full DocumentOscar Tutorial 4
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Instructions:
1. Each member of your group should create his or her own initial structure, with all
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 Spring '11
 SteveHarvey

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