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A Comparison of Pariser-Parr-Pople Calculations on Furan with Nddo(+ University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Fall 1975 A COMPARISON OF PARISER-PARR-POPLE CALCULATIONS ON FURAN WITH NDDO(+ NEGLECT OF DIATOMIC DIFFERENTIAL OVERLAP) CALCULATIONS ON FURAN AND PYRROLE INCLUDING A COMPARISON WITH AB INITIO AND OTHER SEMIEMPIRICAL METHODS DONALD RICHARD LAND University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation LAND, DONALD RICHARD, "A COMPARISON OF PARISER-PARR-POPLE CALCULATIONS ON FURAN WITH NDDO(+ NEGLECT OF DIATOMIC DIFFERENTIAL OVERLAP) CALCULATIONS ON FURAN AND PYRROLE INCLUDING A COMPARISON WITH AB INITIO AND OTHER SEMIEMPIRICAL METHODS" (1975). Doctoral Dissertations. 2349. https://scholars.unh.edu/dissertation/2349 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1.The sign or "target” for pages apparently lacking from the document photographed is "Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below the first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE NOTE: Some pages may have indistinct print. Filmed as received. Xerox University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48106 I 76-2521 LAND, Donald Richard, 1935- A COMPARISON OF PARISER-PARR-POPLE CALCULATIONS ON FURAN WITH NDDO CALCULATIONS ON FURAN AND PYRROLE INCLUDING A COMPARISON WITH AB INITIO AND OTHER SEMIEMPIRICAL METHODS. University of New Hampshire, Ph.D., 1975 Chemistry, general Xerox University Microfilms, Ann Arbor, Michigan 48106 THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED. A COMPARISON OF PARISER-PARR-POPLE CALCULATIONS ON FURAN WITH NDDO CALCULATIONS ON FURAN AND PYRROLE INCLUDING A COMPARISON WITH AB INITIO AND OTHER SEMIEMPIRICAL METHODS by DONALD RICHARD LAND B. S., UNIVERSITY OF CALIFORNIA AT LOS ANGELES, 1959 M. S., HOWARD UNIVERSITY, 1954 A THESIS Submitted to the University of New Hampshire In Partial Fulfillment of The Requirements for the Degree of Doctor of Philosophy Graduate School Department of Chemistry September, 1975 This thesis has been examined and approved. Frank L. Pilar, Thesis Director Professor of Chemistry Alexander R. Amell Professor of Chemistry OjloAJLpLtfL f Clarence L. Grant Professor of Chemistry jL Charles W. Owens Assoc. Professor of Chemistry Robert H. Lambert Professor of Physics Date ACKNOWLEDGEMENT This work is dedicated to my mother, a very strong lady, who somehow, singlehandedly, kept it all together to raise six of us and kept us mostly off the block so we could get some learnin'. Special tribute is paid to those real patriots who have carried on the work of removing the sickness from our country - often forgoing credentials such as these - we have only temporarily parted ways, for the Revolution needs credentials too (e.g. William Kunstler, Dr. Martin Luther King, Dr, W.E.B. DuBois, et al). Special thanks to Dr. Frank Filar who was the reason for my coming to U.N.H. and to Professor Reino Hakala who was instrumental in my getting here. ill TABLE OF CONTENTS LIST OF TABLES vii LIST OF ILLUSTRATIONS viii x:; ABSTRACT I. INTRODUCTION 1 II. HISTORY - THE THESIS IN PERSPECTIVE 9 A, The Pi Electron Approximation 9 B, Pi Electron Methods 11 1. The HMO Method 11 2. The GMS Method 12 3. The PPP Method 14 C. Problems with the Pi Electron Method 16 D. Inclusion of Sigma Electrons - All Electron Methods 19 1. Hoffman's EHT Method 20 2. Complete Neglect of Differential Overlap - the CNDO Approximation 21 3. Neglect of Diatomic Differential Overlap - the NDDO Approximation 23 4. Intermediate Neglect of Differential Overlap - the INDO Approximation 24 5. The Modified INDO Method (MINDO) 26 III. PPP CALCULATIONS ON FURAN - A SUMMARY OF THE CALCULATIONS AND RESULTS 27 1. Pariser-Parr-Pople Equations 27 2. Formulas for|^ and $ 28 iv 3. Configuration Interaction 30 4. Sigma Core Polarization 31 IV. CALCULATIONS ON FURAN AND PYRROLE - THE NDDO METHOD 35 A . Introduction 35 B. The CNDO and NDDO Methods and Equations 3 6 C . Integrals in the NDDO Method 38 D. Basic Parameter Values 41 E. A Brief Description of the Total Program 42 F. Integral Transformations 4? 1. Calculation of the Rotation Angles 5° G. Equations and Procedures 52 V. NDDO RESULTS 56 A. F°, H, P, C and F Matrices for Furan and Pyrrole 56 B. Charges - Hybridization - Charge Migration 56 C. Bond Orders and Bond Populations 6l D. Dipole Moments 65 E. Orbital Energies 67 1. Adjustment of Orbital Energies 67 2. Symmetry of Eigenvectors 68 3 . Orbital Energy Intervals 68 4. Analysis of Orbitals 71 VI. DISCUSSION OF PARAMETERS 74 A. Alternate Parameter Possibilities 74 B. Sensitivity of Charges and Orbital Energies to Changes in and U 75 C. Modification of CNDO Parameters 81 VII. DISCUSSION OF NDDO VS. CNDO AND AB INITIO METHODS 85 v VIII. CONCLUSIONS BIBLIOGRAPHY v i LIST OF TABLES 5-1 Hybridization of Nitrogen and Oxygen 56 5-2 Gross Charges - Summary 58 5-3 Comparison of Furan Charges 59 5-4 Comparison of Pyrrole Charges 60 5-5 Furan Bond Orders 61 5-6 Pyrrole Bond Orders 6l 5-7 Furan Bond Populations 62 5-8 Pyrrole Bond Populations 62 5-9 Comparison of Furan and Pyrrole Pi Bond Orders 63 5-10 Bond Order Differences for Furan and Pyrrole 64 5-11 Bond Population Ratios 65 5-12 Comparison of Dipole Moments 66 5-13 Furan Orbital Energies (adjusted) 69 6-1 Variation of Charge Densities with 77 vli LIST OF ILLUSTRATIONS 4-1 Flow Chart of SCF Procedure 46 4-2 Diatomic Orientation of P Orbitals 47 4-3 Molecular Orientation of P Orbitals 47 4-4 Rotation Angles for P Orbitals 48 4-5 Rotation Angles for Realigning Basis Orbitals 51 4-6 Symmetry Oriented Basis Orbitals 52 4-7 Character Table for the C t v Point Group 55 4-8 Symmetry of C* and TT Molecular Orbitals 55 5-1 Furan Energy Levels 70 6-1 Graphs of Variations of the Charges with the Core Inte­ grals, U 78-80 viii ABSTRACT A COMPARISON OF PARISER-PARR-POPLE CALCULATIONS ON FURAN WITH NDDO CALCULATIONS ON FURAN AND PYRROLE INCLUDING A COMPARISON WITH AB INITIO AND OTHER SEMIEMPIRICAL METHODS by DONALD RICHAfiD LAND PPP calculations axe carried out on furan to predict charge densities, ionization potentials, orbital energies, and excited state energies. Variation of parameters and use of various formulas for reson­ ance and coulomb integrals does not give consistently good excited state energies. The relative alpha and beta carbon charges can be predicted consistent with chemical evidence by accounting for sigma-core polariza­ tion in a qualitative way. It Is concluded that the method cannot be parameterized to give correct results for molecuiles with neteroatoms. In part II of the research, NDDO calculations are carried out on furan and pyrrole. Orbital energies, gross charges, charge migration (hybridization), molecular orbital symmetries, dipole moments, bond orders, bond populations and ionization potentials are calculated. Various results are compared with those from HMO, EHT, CNDO, MINDO, PNDO and ab initio methods. All results (except the ionization potential which is predicted poorly) compare favorably with ab initio results and are generally better than those of other semiempirical methods. Specifically, charge migration, bond population, orbital energy intervals and the bonding properties of Individual moleculax orbitals axe predicted in good agreement with ab initio ix calculations. Dipole moments are in good agreement with experimental values and are better than ab initio values. The relative alpha and beta charges are predicted in agreement with chemical evidence and furan is predicted to be more diene-like than pyrrole. The results are encouraging and further work on the parameterization of the NDDO method is suggested in order to improve the ionization poten­ tial. The method is much easier to set up and requires much less computer time than ab initio methods giving comparable results. x CHAPTER I INTRODUCTION The last 40 years have brought about an extensive amount of quan­ tum-mechanical study on conjugated hydrocarbons, lately Including com­ pounds with heteroatoms, which present special difficulties.
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