Ab initio is a Latin term meaning "from the beginning" and is commonly used in the context of computational chemistry and physics. Ab initio methods refer to theoretical approaches that calculate the properties of complex systems, such as molecules or materials, based solely on the fundamental laws of quantum mechanics, without the need for empirical parameters. Ab initio calculations can provide highly accurate predictions of molecular structures, energies, and other properties, making them valuable tools for understanding chemical reactions, predicting material properties, and designing new molecules with specific properties. These methods typically involve solving the Schrödinger equation using numerical techniques, such as density functional theory or wavefunction-based methods. Overall, ab initio research aims to enhance our understanding of the behavior of atoms and molecules at the quantum level, leading to advancements in various fields, including chemistry, material science, and drug discovery.