Learn the fundamental principles of quantum chemical calculations in this comprehensive lecture that covers the theoretical foundations and practical applications of computational quantum chemistry. Explore the mathematical framework underlying quantum mechanical descriptions of molecular systems, including wave functions, Hamiltonians, and approximation methods used to solve the Schrödinger equation for multi-electron systems. Discover key computational approaches such as Hartree-Fock theory, density functional theory (DFT), and post-Hartree-Fock methods, while understanding their strengths, limitations, and appropriate applications. Gain insights into basis sets, molecular orbital theory, and how to interpret quantum chemical results for predicting molecular properties, reaction mechanisms, and electronic structures. Master the essential concepts needed to begin performing quantum chemical calculations and understand their role in modern computational chemistry research.