fall 09 lm _4 spartan-morse

fall 09 lm _4 spartan-morse - Chem 481L Lab Module #4 Due...

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Chem 481L Fall 2009 Lab Module #4 Potential energy curve for H 2 + Due Date: Noon, Tuesday, September 29 Submit via Blackboard Format: Word document (pertinent analysis imported from Excel/Mathcad) Goals: The goal of this week’s module is to find the parameters of a Morse potential that describes the H 2 + bond. First, you will use Spartan to produce a potential energy curve that describes the relationship between system energy and internuclear distance (bond length) for H 2 +. Next, you will use Mathcad’s genfit function to fit the Spartan data to a Morse potential. Research questions: How well does Spartan approximate the potential energy curve for H 2 +; that is, how well do Spartan-generated potentials correspond to experimental data? How does the choice of basis set inform output in Spartan’s models? With regard to the use of genfit, the research questions are: What is the form of the Morse potential that fits the Spartan PC data; i.e., what are the parameters that describe the potential in a Morse form? How well does this potential correspond to experimental data? Readings: Atkins on Morse potential and Molecular vibrations. Mathcad help manual and quicksheet tutorials about “genfit.” Introduction The Morse potential has form: ( 29 [ ] 2 1 ) ( eq x x a e e D x V - - - = where D e is the well depth, x eq is the equilibrium bond length, and e D k a 2 = ( k is the bond force constant) It is a useful potential when representing the stretching of chemical bonds as its anharmonicity at long bond lengths predicts more realistic behavior than the harmonic oscillator. In particular, it allows for bond dissociation at long bond length while maintaining the harmonic form near the
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This note was uploaded on 03/03/2010 for the course CHEM 431 taught by Professor Pielak during the Spring '07 term at UNC.

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fall 09 lm _4 spartan-morse - Chem 481L Lab Module #4 Due...

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