Binding and diffusion of Al adatoms and dimers on the Si(100)-2 × 1 reconstructed surface: A hybrid QM/MM embedded cluster study

Issue Date

4-2009

Abstract

When group III metals are deposited onto the Si(100)-2 × 1 reconstructed surface they are observed to selfassemble into chains of atoms that are one atom high by one atom wide. To better understand this onedimensional 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 Al-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. © 2009 American Chemical Society.

Source or Periodical Title

Journal of Physical Chemistry C

ISSN

19327447

Volume

113

Issue

17

Page

7277-7289

Document Type

Article

Language

English

Identifier

doi:10.1021/ jp8105937

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