Pseudopotential techniques

Whether one uses an all-electron or a pseudopotential technique, the fundamental aims of a DFT calculation are to calculate the total energy and the charge/spin density of a given configuration of atoms. The Kohn-Sham equation... 

Band structure calculations have been performed with the valence effective Hamiltonian (VEH) nonempirical pseudopotential technique. The VEH method yields one-electron energies of ab initio double-zeta quality and has been demonstrated to provide accurate estimates of essential electronic properties such as ionization potentials (IP), bandwidths (BW), bandgaps (Eg), and electron affinities (EA) in the context of conducting polymers. All the calculations have been carried out using the VEH parameters previously reported for sulfur, oxygen, and nitrogen atoms and those recently obtained for carbon and hydrogen atoms,... 

From a basic point of view, the two purposes are different and should be distinguished one may be tempted to eliminate the core electrons while keeping a non-minimal valence basis set, as occurs in pseudopotential techniques, on the one hand, while on the other hand, one may try to treat a coreless problem such as a cluster of hydrogen atoms in a minimal basis set, or... 

The present paper is organized as follows Section 2 deals with the pseudopotential technique for solving the Schrddinger equation, section 3 derives the stress theorem expressed in reciprocal space within the local-density approximation. Section 4 comments on a number of technical but nevertheless important points in ab-initio calculations. Section 5 deals with calculations on the semiconductors Si, Ge, and GaAs, whose elastic properties is the topic of section 6. 

Pseudopotentials for Molecular Calculations. I. The PSIBMOL Algorithm and Test Cases, (b) P. Durand and J. C. Barthelat, Theor. Chim. Acta, 38, 283 (1975). A Theoretical Method to Determine Atomic Pseudopotentials for Electronic Structure Calculations of Molecules and Solids, (c) G. H. Jeung, J. C. Barthelat, and M. Pelissier, Chem. Phys. Lett., 91, 81 (1982). Minimal-Basis-Adapted Pseudopotentials for Transition Metal Atoms, (d) M. Pelissier and P. Durand, Theor. Chim. Acta, 55,43 (1980). Testing the Arbitrariness and Limits of a Pseudopotential Technique Through Calculations on the Series of Diatoms HF, AlH, HCl, AIF, Fj and Clj. 

A study of the monohydrides, monoxides, and monofluorides of lanthanides and actinides using ab initio all-electron and pseudopotential techniques is also available. The spectroscopic constants of low-lying electronic states of ThO " ... 

More about the all-electron pseudopotential technique can be found in [10] (Fig. 12.1). 

Figure 1 Band structures of BP by (a) total-energy pseudopotential technique within the local density approximation (18), and (b) GW approximation (21).

As in any semiconductors, point defects affect the electrical and optical properties of ZnO as well. Point defects include native defects (vacancies, interstitials, and antisites), impurities, and defect complexes. The concentration of point defects depends on their formation energies. Van de WaHe et al. [86,87] calculated formation energies and electronic structure of native point defects and hydrogen in ZnO by using the first-principles, plane-wave pseudopotential technique together with the supercell approach. In this theory, the concentration of a defect in a crystal under thermodynamic equilibrium depends upon its formation energy if in the following form ... 

As mentioned above, the results discussed below are obtained using Ab initio methods. Other methods used to study QDs are effective mass theory (EMT) and the pseudopotential techniques. EMT uses a particle-in-a-box model where the electron and hole masses are given by their bulk values. EMT is an intuitive description that explains general trends seen in experiments. The atomistic pseudopotential technique can be applied to large systems, but requires careful parameterization for each material. Ab initio approaches use minimal parameterization and are applicable to most materials. This makes them particularly useful for studying dopants, defects, ligands, core/shell systems and QD synthesis. The Hartree-Fock (HE) method and density functional theory (DFT) have been around for many decades, while time domain (TD) DFT and non-adiabatic molecular dynamics (NAMD) are more recent areas of research. Currently, ab initio TDDFT/NAMD is the only... 

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