This book provides an accessible and comprehensive introduction to Density Functional Theory (DFT) and its applications in materials science, with a particular focus on undergraduate students and early-stage researchers. It introduces the fundamental principles of quantum mechanics that underpin DFT, followed by the theoretical development of the method and its practical implementation in computational materials science. The book covers key topics such as the Hohenberg–Kohn theorems, Kohn–Sham equations, exchange–correlation functionals, and practical approaches to performing DFT calculations using widely used computational tools. In addition to the theoretical framework, it highlights important applications of DFT in solid-state physics, surface science, nanomaterials, and material defects. Designed for students in physics, chemistry, materials science, and related disciplines, this book bridges the gap between theory and practice by explaining complex concepts in a clear and structured manner while providing guidance on applying DFT to solve real-world materials problems. It will also serve as a useful reference for researchers beginning their work in computational materials modeling and molecular simulations.

Dr. Roshan Thotagamuge is affiliated with the Department of Optometry, Faculty of Allied Health Sciences, University of Sri Jayewardenepura, Sri Lanka. He has more than twenty years of experience as a scientist, educator, and researcher. His academic work focuses on materials science, nanotechnology, and computational modeling, with particular interest in understanding and improving material properties through both theoretical and experimental approaches. Throughout his career, Dr. Thotagamuge has been actively involved in teaching, research supervision, and scientific collaboration, contributing to the development of interdisciplinary research in materials and nanoscience. His work aims to bridge fundamental scientific theory with practical technological applications.