For the past 30 years density functional theory has been the dominant method for the quantum mechanical simulation of periodic systems. In recent years it has also been adopted by quantum chemists and is now very widely used for the simulation of energy surfaces in molecules. In this lecture we introduce the basic concepts underlying density functional theory and outline the features that have ...

Abstract Chalcopyrite semiconductors are widely used as absorbers in thin film solar cells, especially flexible due to their high power conversion efficiency. They also have interesting mechanical properties, making them promising materials for flexible, light, and cells. In this work, we report the first-principle calculations of lattice constant bulk modulus CuInS 2 , CuInSe CuIn(S,Se) absorb...

The structure of the electronically excited states of 3He and 4He clusters is investigated using fluorescence excitation spectroscopy. Distinct bands are observed energetically close to atomic 1s-ns, nd, np transitions and attributed to perturbed excited He atomiclike states with different principle and orbital quantum numbers. The line shifts and widths of the bands of 3He and 4He clusters of ...

The paper reports computations on endohedral fullerene systems, combining the treatments of quantum chemistry and statistical mechanics. Relative concentrations of five isomers of Ca@C72 are presented as an illustration, using the Gibbs energy based on density-functional theory computations. Anharmonicity effects are probed on a simple model system of C6. The temperature-pressure stabilization ...

The N-(2-benzoyl-phenyl) oxalyl derivatives are important models for studying of three-centered intramolecular hydrogen bonding in organic molecules. The quantum theoretical calculations for two crystal structures of N-(2-benzoyl-phenyl) oxalyl (compounds I and II) were performed by Density Functional Theory (B3LYP method and 6-311+G* basis set). From the optimized structures, geometric paramet...

For the study of geometrical structure, stability, and electronic magnetic properties Germanium tin-doped two-dimensional hexagonal boron nitride (h-BN), First-principles calculations have been carried out. Plane-wave pseudo-potential method in association with density functional theory (DFT) framework used Quantum ESPRESSO codes has implemented to perform calculations. A 3X3 supercell size sub...

A first-principles method, based on density functional perturbation theory, is presented for computing the leading order tunability of high-dielectric-constant materials.