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Summary
Summary
Computational chemistry, including electronic structure modeling, is a fast and accurate tool for treating large chemically meaningful systems. Unique among current quantum chemistry texts, Electronic Structure Modeling: Connections Between Theory and Software enables nonspecialists to employ computational methods in their own investigations.
The text illustrates theoretical methods with numerical detail and model calculations. It clarifies what these modeling programs can do, their known pathologies, which ones are suited for specific kinds of projects, and how to reproduce them using the accompanying PC-LOBE bundled software. While elucidating gradient-based molecular structure optimization, the text reviews notable successes and unsolved problems or failures in electronic structure modeling. It also describes the theory and computation of circular dichroism and optical rotation, including magnetically induced optical phenomena.
Offering an accessible introduction to computational methods, Electronic Structure Modeling permits users to practice modeling with a full understanding of the algorithms that support their calculations.
Author Notes
Trindle, Carl; Shillady, Donald
Table of Contents
Preface | p. xiii |
Authors | p. xvii |
Chapter 1 One-Dimensional Quantum Mechanics: A Short Review | |
The Particle-in-a-Box | p. 3 |
Particle-on-a-Ring | p. 11 |
Operator Algebra in Quantum Mechanics | p. 15 |
Operator Commutation | p. 16 |
Commutation and Uncertainty | p. 17 |
The Harmonic Oscillator | p. 18 |
Summary | p. 20 |
References | p. 20 |
Chapter 2 Matrices, Representations, and Electronic Structure Modeling | |
Definition and Properties of Vectors and Matrices | p. 23 |
Response Matrices | p. 29 |
Symmetry Operations | p. 34 |
Conclusion | p. 35 |
References | p. 35 |
Chapter 3 Methods of Approximation and the SCF Method | |
The Variation Theorem | p. 37 |
The Variational Treatment of the H Atom | p. 38 |
Variational Treatment of the H Atom (Gaussian Trial Function) | p. 39 |
Variation Example with a Linear Combination of Basis Functions | p. 41 |
A Variational Calculation in One Dimension | p. 43 |
Determinantal Wave Functions and HF-SCF Theory | p. 45 |
Determinantal Integrals for One-Electron Operators | p. 48 |
Determinantal Matrix Elements for Two-Electron Operators | p. 49 |
Restricted Form of the Determinant | p. 52 |
Expansion of the RHF Energy in a Basis | p. 54 |
Roothaan-Hartree-Fock Self-Consistent Field Equation | p. 55 |
Koopmans' Theorem | p. 58 |
Brillouin's Theorem | p. 59 |
References | p. 59 |
Chapter 4 Gaussian-Lobe Basis Sets | |
Overlap (S[subscript AB]) | p. 66 |
Kinetic Energy (T[subscript AB]) | p. 67 |
Nuclear Potential (for Z Nuclear Charge Value, at r[subscript C]) | p. 67 |
Electron Repulsion (Coulomb's Law for Two Charge Distributions) | p. 67 |
Dipole Moment | p. 68 |
Quadrupole Moment | p. 70 |
Angular Momentum (Imaginary Hermitian Operator) | p. 71 |
Spin-Orbit and Spin-Spin Interactions | p. 71 |
Frost FSGO Method | p. 72 |
Screened Coulomb Potential | p. 73 |
Electrostatic Potential Maps | p. 74 |
References | p. 75 |
Chapter 5 A Very Simple MO Program | |
Helium in SCF1s | p. 77 |
Beryllium Atom in SCF1s STOs | p. 81 |
Spherical Gaussian Contraction for Helium: 3G Expansion | p. 84 |
Molecular Hydrogen in SCF1s | p. 90 |
LiH-Frost Spherical Gaussian Pairs | p. 92 |
PCLOBE and Sample Output from RHF Calculations | p. 95 |
Li[subscript 2] | p. 95 |
N[subscript 2] | p. 102 |
N[subscript 2], CO, BF: An Isoelectronic Series | p. 108 |
The Value of Mulliken Charges and Mayer Bond Orders | p. 110 |
Bonding in C[subscript 2] and LiF by Natural Bond Order Analysis | p. 110 |
Summary and Conclusions | p. 114 |
References | p. 115 |
Chapter 6 Geometry Optimization and Vibrational Frequencies by SCF | |
Introduction | p. 117 |
The SCF-Roothaan Calculation in PCLOBE | p. 118 |
Geometry | p. 118 |
Basis | p. 119 |
Contraction and Weighting | p. 120 |
Lobe Representations of p Functions | p. 120 |
Symmetry and the Basis | p. 120 |
Overlap Matrix | p. 121 |
Solution of the SCF Equation: Dealing with the Overlapping Basis | p. 121 |
Construct the Core Matrix Representing the Kinetic Energy and Nuclear-Electron Attraction | p. 122 |
Approximate the Fock Matrix and Solve the Secular Equation | p. 122 |
Begin the Iterative Solution of the SCF Equation-Guess MOs | p. 123 |
Symmetry Labeling the MOs | p. 123 |
Evaluate the Density Matrix | p. 124 |
Repulsion Integrals | p. 124 |
Continue the Iteration | p. 126 |
Test for Convergence | p. 126 |
Inspect the Output: MOs and Energies | p. 127 |
Describe the Charge Distribution | p. 128 |
Molecular Structure Determination by Energy Minimization | p. 130 |
Derivative of the Hartree-Fock Energy | p. 130 |
Search Techniques Using the Gradient | p. 132 |
Geometry Optimization in PCLOBE | p. 133 |
Begin with the Steepest Descents Approach to a Minimum | p. 134 |
Second Derivatives of the Hartree-Fock Energy and Vibrational Spectra | p. 136 |
SCF Calculation Revisited: Alternatives and Points of Contention | p. 140 |
Impure Symmetry of Properties Computed in the Contracted Lobe Basis | p. 143 |
Completeness and Linear Dependence in the Lobe Basis | p. 143 |
Management of Two-Electron Integrals | p. 143 |
Assembly of the Fock Matrix | p. 144 |
Convergence of the Iterative Solution | p. 144 |
Reoptimization of Formaldehyde in an Extended Basis | p. 145 |
Historical Landmark: The Accomplishment of Boys | p. 153 |
References | p. 156 |
Chapter 7 Configuration Interaction and Potential Curves | |
Configuration Interaction in General | p. 159 |
Slater Determinant MO-CI | p. 160 |
CI Without Canonical Orbitals | p. 162 |
Pauling Valence Bond and CI | p. 162 |
Boys-Reeves CI (MOVB) | p. 165 |
Resolution of an MOVB-CI Wave Function into Leading Excitations | p. 165 |
Sydnone CI | p. 171 |
CI and Potential Curves | p. 172 |
Three Descriptions of Dissociation of the Hydrogen Molecule | p. 174 |
MOVB-CI for BH | p. 175 |
MOVB-CI of Formaldehyde Dissociation | p. 179 |
MCSCF and CASSCF: Achieving Proper Dissociation for Larger Systems | p. 181 |
Conclusions | p. 184 |
References | p. 185 |
Chapter 8 Perturbation Theory | |
First-Order Correction to a Nondegenerate Reference System | p. 187 |
Second-Order Correction-Nondegenerate Case | p. 189 |
The Morse Potential | p. 192 |
The Degenerate Case | p. 193 |
Perturbation Theory in Approximate MO Theory | p. 196 |
MP2 as Perturbation Theory | p. 198 |
Time-Dependent Perturbation Theory | p. 200 |
Hamiltonian for Matter in an Electromagnetic Field | p. 202 |
Time-Dependent Perturbation Theory for Charged Particles in the Electromagnetic Field | p. 203 |
Length-Velocity Relationship | p. 207 |
Response Theory | p. 209 |
References | p. 210 |
Chapter 9 Highly Accurate Methods: Coupled Cluster Calculations, Extrapolation to Chemical Accuracy, and Quantum Monte Carlo Methods | |
Aspiration to Chemical Accuracy | p. 211 |
An Aerial View of CC | p. 212 |
Theoretical Foundations | p. 213 |
A Notational Convenience: Creation and Annihilation Operators | p. 215 |
Specification of the T Operators | p. 216 |
The Size Consistency Issue in CC and CI | p. 217 |
Solving the CC Equations | p. 219 |
CC-Doubles Approximation | p. 219 |
Imminent Developments | p. 222 |
Beyond CCSD | p. 223 |
Performance of CCSD(T) | p. 224 |
Application to Isomer Energies | p. 232 |
Thermochemical Standards by Quantum Chemistry | p. 235 |
Aspiration to Exact Description: Quantum Monte Carlo Calculations | p. 240 |
Random (?) Numbers | p. 241 |
Anderson's Intuitive Application of Randomness | p. 242 |
An Early Example of Diffusion Quantum Monte Carlo Calculation | p. 244 |
Shortcuts: Pseudopotentials and the Sparse Algorithm | p. 248 |
Formaldehyde (Again) by QMC | p. 248 |
Conclusion | p. 250 |
References | p. 251 |
Chapter 10 Modeling the Coulomb Hole | |
The Fermi Hole and Exchange-Correlation | p. 256 |
Coulomb Correlation Hole | p. 256 |
Applying the Correlated-SCF Method to Hydroxylamine | p. 265 |
Summary | p. 267 |
References | p. 267 |
Chapter 11 Density Functional Theory | |
Introduction | p. 269 |
John Perdew's Ladder | p. 270 |
Early Forms of Density Functional Theory: Gill's History | p. 271 |
Thomas-Fermi-Dirac Theory | p. 271 |
The Hohenberg-Kohn Existence Theorem | p. 273 |
Kohn-Sham Procedure for Finding the Density | p. 274 |
DFT and SCF Calculations Have Common Features | p. 275 |
Search for the Functionals | p. 276 |
The Idea of the Hole | p. 277 |
Evaluating the DFT Energy Using Functionals (Slater) | p. 278 |
More on the Local Density Approximation's Hole | p. 279 |
Refinements to the VWN Exchange-Correlation Functionals | p. 280 |
Perdew Functionals | p. 280 |
Becke Functionals | p. 282 |
Lee-Yang-Parr Correlation | p. 283 |
The Adiabatic Connection and Hybrid Functionals | p. 284 |
Becke 1995-Impact of Imposing Constraints | p. 286 |
PBE Exchange-Correlation Functional | p. 288 |
Correlation Effects on Kinetic Energy | p. 293 |
TPSS Functional | p. 295 |
The Empirical Thread | p. 299 |
The Zhao-Truhlar M06-L DFT Functional | p. 300 |
M06-L Meta-GGA Correlation Functional | p. 301 |
Position-Dependent Exchange | p. 304 |
The Iterative Localized Local Hybrid Method, LLH | p. 308 |
Gridless! | p. 310 |
Resolution of the Identity | p. 310 |
A Gridless DFT Method Using Least-Squares Slater Exchange | p. 312 |
Slater-Roothaan SCF | p. 313 |
Two DFT-Focussed Programs | p. 315 |
The Amsterdam Density Functional Suite | p. 315 |
SAOP: A Fourth-Rung Exchange-Correlation Model for Excitations | p. 316 |
deMon2k | p. 319 |
Summary, Conclusions, and Overview | p. 330 |
Appendix: Technical Aspects of DFT Calculations | p. 333 |
Grid-Mesh Integration in DFT Programs | p. 333 |
Representation of the Density by Auxiliary Basis Functions | p. 335 |
Appendix References | p. 338 |
References | p. 339 |
Chapter 12 Calculation of Nuclear Magnetic Resonance Shielding/Shifts | |
Introduction | p. 343 |
Ramsey Theory | p. 344 |
Challenges to Use of Ramsey's Form | p. 345 |
Excitations | p. 345 |
Gauge Origin | p. 346 |
Semiempirical Adaptions of Ramsey's Formalism | p. 346 |
Ditchfield's Formalism | p. 347 |
Coupled Perturbed Hartree-Fock Method | p. 350 |
First Results of Calculations in Ditchfield's Formulation | p. 352 |
Ditchfield's Formulation in GAMESS | p. 353 |
Runtype | p. 354 |
Basis | p. 355 |
Already Familiar! | p. 359 |
Charge Analysis | p. 359 |
Timing | p. 360 |
NMR Report | p. 360 |
Ditchfield's Formulation in GAUSSIAN-03 | p. 361 |
Use of Localized Orbitals in NMR-Shielding Calculations | p. 361 |
Individual Gauge for Local Orbitals | p. 362 |
RPAC Program (LORG) | p. 363 |
Subtleties of Orbital Localization | p. 367 |
Correlation Corrections and NMR Shielding: DFT | p. 368 |
GAUSSIAN-03 NMR Shifts: DFT-Based Values of Shielding | p. 369 |
CSGT Method (Continuous Set of Gauge Transformations) | p. 370 |
Practical Use of Calculated Chemical Shifts | p. 372 |
Chemical Shifts of Taxol | p. 374 |
Advances in DFT-Based NMR | p. 375 |
Keal and Tozer | p. 375 |
Arbuznikov et al. | p. 377 |
The Question of Coupling and Fine Structure | p. 380 |
Perturbative Correlation-Corrected Methods for Shielding | p. 381 |
ACES-II Coupled Cluster Calculation of NMR Properties | p. 382 |
Conclusion | p. 386 |
References | p. 386 |
Predicting Magnetic Properties with ChemDraw and Gaussian | p. 388 |
Chapter 13 The Representation of Electronically Excited States | |
Introduction | p. 389 |
CI-Singles | p. 389 |
Practical Use of the CIS Equations | p. 391 |
Singlet and Triplet State Energies for the 1G Model | p. 392 |
PCLOBE Illustration of CIS | p. 394 |
Structural Relaxation in the Excited State | p. 400 |
Case Study for Formaldehyde | p. 401 |
Correlation Corrections | p. 402 |
Time-Dependent Hartree-Fock Treatments of Excitations | p. 403 |
Formaldehyde Again | p. 404 |
A Case Study-Sulfur Dioxide | p. 405 |
Adaptation of the Time-Dependent Formalism to DFT | p. 407 |
Applications | p. 409 |
Sulfur Dioxide in TD-DFT | p. 409 |
Pyridine in TD-B3LYP | p. 410 |
Pyrrole in B3LYP-DFT | p. 411 |
Substituted Aniline | p. 412 |
CCSD-EOM Treatment of Excited States | p. 413 |
Conclusions | p. 414 |
References | p. 415 |
Chapter 14 Circular Dichroism and Optical Rotatory Dispersion | |
The Phenomenon of Optical Rotation | p. 417 |
PCLOBE Modeling of CD Spectra | p. 421 |
Examples of CD/ORD Computations with PCLOBE | p. 422 |
[alpha]-Pinene | p. 426 |
Ways to Improve CD and ORD Calculations | p. 433 |
Use GIAOs | p. 433 |
Use Linear Response Theory | p. 434 |
Use Correlation-Corrected Methods (Time-Dependent DFT, CCSD) | p. 435 |
Methyloxirane: A Hard Case | p. 435 |
Optical Rotatory Dispersion for Methyloxirane | p. 437 |
Experimental Data and Advanced Calculations for Methyloxirane | p. 439 |
A Brighter View | p. 442 |
Specific Examples | p. 443 |
The Phenomenon of Magnetic Circular Dichroism | p. 447 |
Theory of MCD | p. 448 |
PCLOBE Modeling of Rings | p. 450 |
Formaldehyde MCD | p. 451 |
CIS Output: Excited States | p. 456 |
MCD-A Challenge to Modern Theory | p. 465 |
Note on Units for Optical Activity | p. 468 |
Summary and Conclusions | p. 470 |
Acknowledgments | p. 470 |
References | p. 471 |
Index | p. 473 |