Details

Autor(en) / Beteiligte

• Black, Suely Meth

Titel

1.~Correlated ab initio calculations of the adsorption of methyl halide and hydrogen halide molecules on the gallium arsenide(110) surface, and, 2.~Charge density fitting for calculation of the Hartree-Fock Coulomb matrix

Ort / Verlag

ProQuest Dissertations Publishing

Erscheinungsjahr

1996

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• (1). The effects of the semiconductor cluster size and structure in ab initio calculations of binding energy and geometry of HX and MeX (X=Cl,Br,I) on the GaAs(110) surface have been studied with the use of Localized second-order Moller-Plesset (LMP2), and Gradient-Corrected Density Functional Theory (GCDFT). The GaAs(110) surface has been represented by clusters of different sizes and geometries, containing up to three layers, with the cluster dangling bonds saturated with hydrogen atoms. The degree of agreement of the results obtained with the two computational methods vary only slightly with the cluster size. The position and geometry of the adsorbate on the cluster were determined by constrained structure optimization using analytic gradients to minimize the GC-DFT energy of the compound system. The LMP2 energy of the CG-DFT optimal structure has also been calculated. Reasonable agreement with experimental results are obtained both for the binding energy and the orientation angle of the adsorbate on the surface. 2). The pseudospectral program PS-GVB has been modified to test the viability of using fitted charge density in the calculation of the Hartree-Fock Coulomb matrix. This approximation leads to savings, both in the number of integrals that must be calculated, and in the transformation of the integrals from atomic to molecular orbitals. Large number of tests have been performed for a group of six molecules containing C, O and H, using the small 3-21G basis sets. The influence of the physical grid, fitting basis sets and fitting operator has been studied. Our first assessment leads us to believe in the feasibility of the proposed method as a routine to shorten the calculation of the Hartree-Fock Coulomb matrix.