Total Energy and Structural Properties

We have employed a density-functional tight-binding (DFTB) scheme for the calculation of the total energy and several properties of a wide range of MOF crystal structures. Periodic boundary conditions (PBC) have been used to represent the infinite framework of the solid state. Lattice parameters and MOF structures have been fully optimized. The number of k points was determined by reaching convergence with respect to the total energy. 

The present method focuses on solving Kohn Sham equations and calculating electronic states, total energy and material properties of non-crystalline, nonperiodic structures. Contrary to the variety of well established k-space methods that are based on Bloch s theorem and applicable to periodic structures, we don t assume periodicity in any respect. Precise ab-initio environment-reflecting pseudopotentials proven within the plane wave approach are connected with real space finite-element basis in the present approach. The main expected asset of the present approach is the combination of efficiency and high precision of ab-initio pseudopotentials with universal applicability, universal basis and excellent convergence control of finite-element method not restricted to periodic environment. 

Jansen H J F and Freeman A J 1984 Total-energy full-potential linearized augmented plane-wave method for bulk solids electronic and structural properties of tungsten Phys. Rev. B 30 561-9... 

MO calculations can provide the minimum-energy structure, total energy, and overall electron density of a given molecule. However, this information is in the form of the sum of the individual MOs and cannot be easily dissected into contributions by specific atoms or groups. How can the properties described by the MOs be related to our concept of molecules as a colleetion of atoms or functional groups held together by chemical bonds ... 

The basic concepts of the one-electron Kohn-Sham theory have been presented and the structure, properties and approximations of the Kohn-Sham exchange-correlation potential have been overviewed. The discussion has been focused on the most recent developments in the theory, such as the construction of from the correlated densities, the methods to obtain total energy and energy differences from the potential, and the orbital dependent approximations to v. The recent achievements in analysis of the atomic shell and molecular bond midpoint structure of have been... 

---