Quantum chemistry is a branch of theoretical chemistry which applies quantum mechanics and quantum field theory to address problems in chemistry. One application of quantum chemistry is the electronic behavior of atoms and molecules relative to their chemical reactivity. Quantum chemistry lies on the border between chemistry and physics. Thus, significant contributions have been made by scientists from both fields. It has a strong and active overlap with the field of atomic physics and molecular physics, as well as physical chemistry. Quantum chemistry is based on the postulates of Quantum Mechanics. The theory of quantum chemistry with an emphasis on their practical implications for the molecular modeller, and we will try to answer the questions of when to use a quantum chemical method instead of molecular mechanics, which quantum chemical method to choose, and what to expect from the quality of the results.
