skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Defective pyrite (100) surface: An ab initio study

Abstract

The structural and electronic properties of sulfur monomeric defects at the FeS{sub 2}(100) surface have been studied by periodic density-functional calculations. We have shown that for a monomeric sulfur bound to an originally fivefold coordinated surface Fe site, the defect core features a triplet electronic ground state with unpaired spins localized on the exposed Fe-S unit. At this site, the iron and sulfur ions have oxidation states +4 and -2, respectively. This defect can be seen as produced via heterolytic bond breaking of the S-S sulfur dimer followed by a Fe-S redox reaction. The calculated sulfur 2p core-level shifts of the monomeric defects are in good agreement with experimental photoemission spectra, which allow a compelling assignment of the different spectroscopic features. The effect of water on the stability of the defective surface has also been studied, and it has been shown that the triplet state is stable against the wetting of the surface. The most important implications of the presence of the monomeric sulfur defect on the reactivity are also discussed.

Authors:
 [1];  [2];  [3]
  1. Institute of Structural Chemistry, Chemical Research Center, P.O. Box 17, Budapest 1525 (Hungary)
  2. Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Cozzi 53, I-20125 Milano (Italy)
  3. Computational Science, Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, Via Giuseppe Buffi 13, 6900 Lugano (Switzerland)
Publication Date:
OSTI Identifier:
20957821
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 16; Other Information: DOI: 10.1103/PhysRevB.75.165406; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DEFECTS; DENSITY FUNCTIONAL METHOD; GROUND STATES; IRON; IRON SULFIDES; PHOTOELECTRON SPECTROSCOPY; PHOTOEMISSION; PYRITE; REDOX REACTIONS; SPIN; SULFUR; SULFUR IONS; SURFACES

Citation Formats

Stirling, Andras, Bernasconi, Marco, and Parrinello, Michele. Defective pyrite (100) surface: An ab initio study. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.165406.
Stirling, Andras, Bernasconi, Marco, & Parrinello, Michele. Defective pyrite (100) surface: An ab initio study. United States. doi:10.1103/PHYSREVB.75.165406.
Stirling, Andras, Bernasconi, Marco, and Parrinello, Michele. Sun . "Defective pyrite (100) surface: An ab initio study". United States. doi:10.1103/PHYSREVB.75.165406.
@article{osti_20957821,
title = {Defective pyrite (100) surface: An ab initio study},
author = {Stirling, Andras and Bernasconi, Marco and Parrinello, Michele},
abstractNote = {The structural and electronic properties of sulfur monomeric defects at the FeS{sub 2}(100) surface have been studied by periodic density-functional calculations. We have shown that for a monomeric sulfur bound to an originally fivefold coordinated surface Fe site, the defect core features a triplet electronic ground state with unpaired spins localized on the exposed Fe-S unit. At this site, the iron and sulfur ions have oxidation states +4 and -2, respectively. This defect can be seen as produced via heterolytic bond breaking of the S-S sulfur dimer followed by a Fe-S redox reaction. The calculated sulfur 2p core-level shifts of the monomeric defects are in good agreement with experimental photoemission spectra, which allow a compelling assignment of the different spectroscopic features. The effect of water on the stability of the defective surface has also been studied, and it has been shown that the triplet state is stable against the wetting of the surface. The most important implications of the presence of the monomeric sulfur defect on the reactivity are also discussed.},
doi = {10.1103/PHYSREVB.75.165406},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 16,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • Ga- and As-terminated GaAs(100) surfaces are studied through first-principles density-functional pseudopotential calculations of the energies of surfaces with different stoichiometries and reconstructions. We predict structural transitions as a function of Ga and As chemical potentials within an experimentally accessible range which is shown to be fixed by the bulk energies of Ga, As, and GaAs. The bulk energies are determined accurately by the ab initio calculations. The predicted surface stoichiometries are in good agreement with experimental data.
  • It is known that hydrogen stabilizes the growing diamond surface under chemical vapor deposition conditions, but a detailed, stepwise, atomic level understanding of how hydrogen atoms function in the growth mechanism is still missing. In the present work ab initio molecular orbital theory is used to address the structures and energetics of hydrogen atoms on dimer-reconstructed diamond (100)2x1 surfaces. These surfaces are modeled with clusters consisting of nine carbon atoms in four separate layers, which form the basic structural unit of the diamond lattice. Lattice constraints are modeled in the clusters in two different ways in order to determine lowermore » and upper bounds for HC-CH, HC-C and C[double bond]C dimer bond lengths, carbon-hydrogen bond dissociation energies, [pi] bond strengths, and dehydrogenation energies on diamond (100)2x1 surfaces. Calculated lower and upper bounds for the dimer bond lengths are 1.58-1.71 angstroms on the monohydrogenated (100)2x1 surface, 1.55-1.68 angstroms on the surface comprising HC-C radicals, and 1.38-1.44 angstroms on the clean (100)2x1 surface. 122 refs., 3 figs., 7 tabs.« less
  • This work addresses mechanistic issues in halogen assisted diamond growth via ab initio molecular orbital calculations on halogenated and hydrohalogenated carbon clusters as models of dimer-reconstructed diamond (100)2x1 surfaces. The bond lengths and the C-X and XCC-H bond energies have been found along with the effects of lattice constraints. The present results indicate that adsorbed F and Cl should be rather strongly bound to diamond surfaces, at least in the low coverage limit. A comparison of the C-X bond energies with experimental measurements of the stability of adsorbed F and Cl leads to the conclusion that the surface C-X bondmore » strength is greatly reduced at monolayer coverage, due to steric and/or electronic repulsion effects that cannot be adequately included in small cluster models. 60 refs., 3 figs., 8 tabs.« less
  • Mechanisms of dissociative adsorption of a hydrogen molecule and migration of a hydrogen atom on the MgO(100) surface were investigated by means of the ab initio molecular orbital method using a Mg{sub 4}O{sub 4} cluster model. For adsorption, both the homolytic path resulting in two O-H bond formation and the heterolytic path resulting in Mg-H and O-H bond formation were found to give stable products, but only the latter reaction proceeded with no activation energy. The second H{sub 2} molecule was adsorbed attractively to the site adjacent to the Mg-H and O-H bonds. The optimized Mg{sub 4}O{sub 4}H{sub 4} structuremore » had C{sub 2v} symmetry, which suggested a possibility of H{sub 2}-D{sub 2} exchange reaction among adsorbed hydrogen atoms.« less
  • We identify the binding sites for adsorption of a single Ge atom on the Si(100) surface using [ital ab] [ital initio] total-energy calculations. The theoretical diffusion barriers are in excellent agreement with experimental estimates. Using a large supercell we resolve the controversy regarding the binding geometry and migration path for the adatom, and investigate its influence on the buckling of Si dimers. We find that the adatom induces a buckling defect that is frequently observed using scanning tunneling microscopy, indicating that the study of a single adatom may be experimentally accessible.