Intended for beginning graduate and advanced undergraduate courses in Quantum Chemistry. Integrating many new computer-oriented examples and problems throughout, this best-selling, easy-to-understand modern introduction to quantum chemistry covers quantum mechanics, atomic structure, and molecular electronic structure. Practical for students in all branches of chemistry, it offers a solid understanding of quantum mechanics and clearly demonstrates the usefulness and limitations of current quantum-mechanical methods for the calculation of molecular properties. Features: NEW-Substantially increased coverage of computer applications-Shows students how to use the Numerov method to numerically solve the one-dimensional Schr-dinger equation using a BASIC program or a spreadsheet such as Excel, and includes homework problems that ask students to perform molecular calculations. NEW-Updated discussions of molecular electronic structure calculations-Discusses in detail conformational searching (Section 15.12); molecular electrostatic potentials and atomic charges (Section 15.8); and calculation of solvent effects (Section 15.22 and Section 16.7); has greatly expanded treatments of density functional theory (Section 15.20); geometry optimization (Section 15.11); the MNDO, AM1, and PM3 methods (Section 16.5); and molecular mechanics (Section 16.6). Solid presentation of the mathematics needed for quantum chemistry-Explains difficult or subtle points in detail rather than glossing over them, and includes thorough, unintimidating treatments of operators, differential equations, simultaneous linear equations, and other areas of required math. Derivations presented in full, step-by-step detail. Comprehensive coverage of recent, revolutionary advances in modern quantum-chemistry methods for calculating molecular electronic structure-Discusses the ab initio and semiempirical methods for molecular calculations and gives a comprehensive comparison of the accuracy of these methods for calculations of many molecular properties. Extensive problem sets-Contains over 500 problems, with answers provided for nearly all the numerical problems. Includes chapter summaries, worked-out examples, and a bibliography. Contents The Schr-dinger Equation. The Particle in a Box. Operators. The Harmonic Oscillator. Angular Momentum. The Hydrogen Atom. Theorems of Quantum Mechanics. The Variation Method. Perturbation Theory. Electron Spin and the Pauli Principle. Many-Electron Atoms. Molecular Symmetry. Electronic Structure of Diatomic Molecules. The Virial Theorem and the Hellmann-Feynman Theorem. Ab Initio and Density-Functional Treatments of Molecules. Semiempirical and Molecular-Mechanics Treatments of Molecules. Comparisons of Methods.