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Geometry Optimization Lab Activity
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 Scientists use three measurements to define a molecule's geometry:
 Bond Angles (measured in degrees)
 Bond Lengths (measured in angstroms)
 Dihedral Angles (measured in degrees)
 The optimal geometry of a molecule is the geometry that corresponds to the
lowest single point energy calculation of the molecule.
 Potential Energy Surfaces (PES) are
mathematical representations of various geometries and their
corresponding single point energies.
 PES can be used to find quick estimates of the optimal molecular geometry
by locating the minimum point
on the graph.
 Computer programs that calculate optimal molecular geometries use three types of calculations:
 Molecular Mechanics
 SemiEmpirical
 ab initio
 In order to run a geometry optimization on the computer, you must enter an
initial set of cartesian coordinates and a basis set.
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