Density-functional tight-binding: basic concepts and applications to molecules and clusters.

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Mechanics

Background:

• Density Functional Theory (DFT) provides accurate electronic structure calculations but is computationally expensive.
• The Tight Binding (TB) method offers a simpler, faster approach but often lacks accuracy.
• Density Functional based Tight Binding (DFTB) combines the strengths of both DFT and TB.

Purpose of the Study:

• To provide a comprehensive overview of the Density Functional based Tight Binding (DFTB) method.
• To discuss the fundamental principles and standard formulation of DFTB.
• To review recent methodological advancements and diverse applications of DFTB.

Main Methods:

• Standard second-order expansion of DFTB.
• Third-order expansion for improved accuracy.
• Inclusion of non-covalent interactions and self-interaction error correction schemes.
• Time-dependent DFTB for excited states.
• Hybrid DFT/DFTB and DFTB/Molecular Mechanics (MM) schemes.
• Fragment decomposition for large systems.
• Molecular dynamics simulations for potential energy landscapes.
• Non-adiabatic dynamics calculations.

Main Results:

• DFTB accurately describes various systems, including small and large molecules, biomolecules, and clusters.
• DFTB enables the study of diverse properties like vibrational spectroscopy, thermodynamics, and fragmentation.
• Methodological developments extend DFTB's applicability to excited states and complex dynamics.

Conclusions:

• DFTB is a versatile and efficient method for a wide range of chemical and material science problems.
• Ongoing developments continue to expand the scope and accuracy of DFTB.
• DFTB serves as a powerful tool for exploring molecular properties and dynamics.