Chun C. Lin

Self-interaction correction for energy band calculations: Application to LiCl

Abstract We present a method for incorporating the self-interaction correction (SIC) to the local density approximation in energy-band calculations of crystals. A periodic SIC potential is derived using the Wannier representation. The method is applied to a LiCl crystal yielding remarkable improvement in band gap and core levels. Comparison of the computed density of states is made with photoemission work.

On the cluster approach for calculating electronic energies of solid surfaces

Abstract A scheme for calculating electronic energy states of infinite solid surface systems by a cluster approach under the framework of the method of linear combinations of atomic orbitals is presented. The basis functions consist of atomic-like orbitals confined within a cluster whereas the Hamiltonian is that of the infinite solid. The latter circumvents the difficulty arising from the auxiliary boundary of the cluster which is not the true surface of the solid. All the multicenter integrals appearing in the Hamiltonian matrix can be evaluated exactly by means of the technique of Gaussian orbitals. This cluster-basis method is applied to the chlorine-adsorbed silicon (111) surface using several different clusters. The results are compared with those of the same Hamiltonian with basis functions extending over the entire solid in the Bloch-sum form. Criteria for optimal selection of clusters are suggested.

Recent Developments in Applying and Extending the Method of Tight Binding (LCAO) to Energy-Band Calculations

The purpose of this paper is to investigate the computational aspects of the method of tight binding and is roughly divided into two parts. In the first part we present the formulation and application of the tight-binding problem in its most rigorous and straight-forward form without introducing any numerical approximations and then examine the effects of the “nearest-neighbor approximation” which was frequently employed within this scheme to reduce the computational complexity. The second part is devoted to investigating various methods for increasing the variational freedom over that of the traditional minimal basis set and to examining the versatility and applicability of this method to a broad spectrum of crystalline materials.

Electronic states of an isolated phosphorus atom in an amorphous silicon matrix

We study the electronic states of an isolated p atom in an amorphous silicon matrix in several possible bonding configurations. Cluster type of electronic structure calculations are performed on local bonding structures of PSi3 and PSi4 embedded in a random network of a‐Si. The local density of states of P and nearby Si atoms are extracted. For PSi3, we find a dominating P peak about 4 eV below the valence band edge which is consistent with photoemission experiment. The PSi5 results show more structures and differ significantly from the photoemission data. The results for PSi4 are qualitatively similar to those for PSi3.

STRUCTURAL MODELS FOR AMORPHOUS TRANSITION METAL BINARY ALLOYS

A dense random packing of 445 hard spheres with two different diameters in a concentration ratio of 3:1 was hand-built to simulate the structure of amorphous transition metal-metalloid alloys. By introducing appropriate pair potentials of the Lennard-Jones type, the structure is dynamically relaxed by minimizing the total energy. The radial distribution functions (RDF) for amorphous Fe0.75P0.25, Ni0.75P0.25, Co0.75P0.25 are obtained and compared with the experimental data. The calculated RDF’s are resolved into their partial components. The results indicate that such dynamically constructed models are capable of accounting for some subtle features in the RDF of amorphous transition metal-metalloid alloys.

Electronic energy states of amorphous and polycrystalline silicon

An ab initio calculation of the electronic structure in amorphous silicon based on Henderson’s 61‐atom quasiperiodic lattice model has been made by using the method of linear combinations of atomic orbitals. The use of the Gaussian technique makes it quite easy to evaluate all the necessary multicenter integrals and the lattice summation is carried out to convergence. The calculated density of states is in good agreement with experiments. The band structures of silicon in two polycrystalline forms have been calculated also by the same method. Comparison of their density of states with that of amorphous silicon is discussed with special reference to distortion from the perfect tetrahedral coordination.