Rainey_Experiment 3

Rainey_Experiment 3 - Experiment 3 Computational Quantum...

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Experiment 3: Computational Quantum Mechanics Author: Ben Rainey Group 3 Section 1, M 1:25 PM – 4:25 PM Partner: Mark Kalata February 7, 2011
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Experiment 3: Computational Quantum Mechanics Abstract : In this experiment, there were 3 main sub-experiments, all using QM software to accomplish their respective goals. The main objective of experiment 1 was to generate the potential energy curve for the HCl molecule. The dissociation energy of HCl was determined to be 587 kJ/mol, and the vibrational frequency was determined to be 2,966 cm -1 . Literature values for the dissociation energy and vibrational frequency were 431±65 kJ/mol, and 3,000 cm -1 , respectively. The main objective of experiment 2 was to use QM software (Avogadro and GamessQ) to determine the structure, vibrational frequencies, normal modes, and thermodynamic quantities of CO 2 . The vibrational frequencies that were IR-active were determined to be 593 cm -1 and 2258 cm -1 . It was determined that CO 2 has 4 normal modes. Thermodynamic quantities, along with standard literature values, are contained within the report. The main objective of experiment 3 was to apply computational quantum-mechanics to calculate the enthalpy and Gibbs free energy of CO 2 , O 2 , H 2 O, and CH 4 . The enthalpy of combustion of methane was also determined. The numerical results of experiment 3 are contained within the report. Overall, experimental results agreed with literature values within 15%, with few exceptions. It was concluded that QM software is an accurate method of analyzing molecules. I. Introduction This experiment contained three individual experiments. The overall goal of the experiments was to give the user an overview of the capabilities of computational quantum mechanics methods and to provide the user with knowledge about how to apply computational quantum mechanics methods to obtain useful information and solve problems. The experiments employ the use of Avogadro, a cross-platform software application for building and editing molecules. Quantum-chemical calculations were then performed using the General Atomic and Molecular Electronic Structure System (GAMESS). For these experiments GAMESS was set to perform these calculations using ab initio methods and semi-empirical methods. Experiment 1: Morse Oscillator/HCl The main objective of experiment 1 is to generate the potential energy curve for the HCl molecule. This curve is then used to determine the dissociation energy, vibrational frequency, and optimized bond length of HCl. Equation (1) is one method of determining the dissociation energy, D e : = ( - - - ) Vr De 1 e ar re 2 (3-1) where V(r) is the potential energy, D e is the dissociation energy, r is the distance between the atoms, r e is the equilibrium bond distance, and a controls the width of the potential. Equation (2) and Equation (3) are used to determine the vibrational frequency, v : = Vx 12kx2 (3-2) where V(x) is the spring potential, k is the force constant, and x is the length of the elongated
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This note was uploaded on 03/08/2011 for the course CHEM 232 taught by Professor James during the Spring '11 term at Clemson.

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Rainey_Experiment 3 - Experiment 3 Computational Quantum...

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