Binding and Diffusion of Al Adatoms and Dimers on the Si(100)-2 x 1 Reconstructed Surface: A Hybrid QM/MM Embedded Cluster Study

TitleBinding and Diffusion of Al Adatoms and Dimers on the Si(100)-2 x 1 Reconstructed Surface: A Hybrid QM/MM Embedded Cluster Study
Publication TypeJournal Article
Year of Publication2009
AuthorsZorn DD, Albao MA, Evans JW, Gordon MS
Journal TitleJournal of Physical Chemistry C
Volume113
Pages7277-7289
Date Published04/30
ISBN Number1932-7447
Accession NumberISI:000265529700058
Keywordsab-initio cluster, adsorption, cycloaddition reactions, energy minimization, low-coverage phases, mm3 force-field, molecular-mechanics, scanning-tunneling-microscopy, self-consistent-field, si(001) surface
Abstract

When group III metals are deposited onto the Si(100)-2 x 1 reconstructed surface they are observed to self-assemble into chains of atoms that are one atom high by one atom wide. To better understand this one-dimensional island growth, ab initio electronic structure calculations on the structures of Al atoms on silicon clusters have been performed. Natural orbital occupation numbers show that these systems display significant diradical character, suggesting that a multireference method is needed. A multiconfiguration self-consistent field (MCSCF) calculation with a 6-31G(d) basis set and effective core potentials was used to optimize geometries. The surface integrated molecular orbital molecular mechanics embedded cluster method was used to take the surface chemistry into account, as well as the structure of an extended surface region. Potential energy surfaces for binding of Al adatoms and At-Al dimers on the surface were determined, and the former was used to obtain a preliminary assessment of the surface diffusion of adatoms. Hessians were calculated to characterize stationary points, and improved treatment of dynamic electron correlation was accomplished using multireference second order perturbation theory (MRMP2) single-point energy calculations. Results from the MRMP2//MCSCF embedded cluster calculations are compared with those from QM-only cluster calculations, embedded cluster unrestricted density functional theory calculations, and previous Car-Parrinello DFT studies.

URL<Go to ISI>://000265529700058
DOI10.1021/Jp8105937