Evolutionary approach for finding the atomic structure of steps on stable crystal surfaces

Briggs, Ryan M.; Ciobanu, Cristian V.

doi:10.1103/physrevb.75.195415

Cited by 19 publications

(13 citation statements)

References 34 publications

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“…[55][56][57] Monte Carlo techniques have been traditionally used to find cluster geometries 58 and have been recently extended to find surface reconstructions. 59,60 Unfortunately, these methods are computationally very expensive and require long simulations with thousands of evaluations of the system energy ͑and interatomic forces in some cases͒. In particular, genetic algorithms are very powerful but typically need hundreds of generations, in which each one contains tens of trial geometries.…”

Section: B Strategy Of the Structural Searchmentioning

confidence: 99%

Systematic investigation of the structure of the Si(553)-Au surface from first principles

Riikonen

Sánchez‐Portal

2008

Phys. Rev. B

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We present here a comprehensive search for the structure of the Si͑553͒-Au reconstruction. More than 200 different trial structures have been studied using first-principles density-functional calculations with the SIESTA code. An iterative procedure, with a step-by-step increase in the accuracy and computational cost of the calculations, was used to allow for the study of this large number of configurations. We have considered reconstructions restricted to the topmost bilayer and studied two types: ͑i͒ "flat" surface-bilayer models, where atoms at the topmost bilayer present different coordinations and registries with the underlying bulk, and ͑ii͒ nine different models based on the substitution of a silicon atom by a gold atom in different positions of a -bonded chain reconstruction of the Si͑553͒ surface. We have developed a compact notation that allows us to label and identify all these structures. This is very useful for the automatic generation of trial geometries and for counting the number of inequivalent structures, i.e., structures that have different bonding topologies. The most stable models are those that exhibit a honeycomb-chain structure at the step edge. One of our models ͑model "f2"͒ reproduces the main features of the room temperature photoemission and scanning-tunneling microscopy data. Thus, we conclude that this model is a good candidate for the high temperature structure of the Si͑553͒-Au surface.

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Section: B Strategy Of the Structural Searchmentioning

confidence: 99%

Systematic investigation of the structure of the Si(553)-Au surface from first principles

Riikonen

Sánchez‐Portal

2008

Phys. Rev. B

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“…It is not possible to enumerate all the reasonable reconstruction models just from chemical intuition. There have been a few efforts towards automatic prediction of the most stable configuration for either a given stoichiometry [6][7][8] , or a variable composition at constant chemical potential 9 . With these structural models available, the thermodynamical phase diagram can be constructed 10 .…”

Section: Introductionmentioning

confidence: 99%

Evolutionary method for predicting surface reconstructions with variable stoichiometry

et al. 2013

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We present a specially designed evolutionary algorithm for the prediction of surface reconstructions. This new technique allows one to automatically explore all the low-energy configurations with variable surface atoms and variable surface unit cells through the whole chemical potential range. The power of evolutionary search is demonstrated by the efficient identification of diamond 2×1 (100) and 2×1 (111) surfaces with a fixed number of surface atom and a fixed cell size. With further variation of surface unit cells, we study the reconstructions of the polar surface MgO (111). Experiment has detected an oxygen trimer (ozone) motif (Plass et al, 1998). We predict a new version of this motif which can be thermodynamically stable at extreme oxygen rich condition. Finally, we perform a variable stoichiometry search for a complex ternary system: semi-polar GaN (1011) with and without adsorbed oxygen. The search yields a non-intuitive reconstruction based on N3-trimers. These examples demonstrate that an automated scheme to explore the energy landscape of surfaces will improve our understanding of surface reconstructions. The method presented in this report can be generally applied to binary and multi-component systems.

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“…The numerous degrees of freedom involved in exploring large reconstructed or stepped surfaces makes the search for the correct model particularly difficult. Systematic total-energy simulations [15], Monte Carlo methods [41], and even genetic algorithms [42]-all of which require intensive computational resources-are appearing more frequently. RAS may offer significant advantages in the search for new models of anisotropic surface structures.…”

Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 23 Augusmentioning

confidence: 99%

Optical Fingerprints of Si Honeycomb Chains and Atomic Gold Wires on the Si(111)-(5×2)-Au Surface

Hogan

Ferraro²,

McAlinden

et al. 2013

Phys. Rev. Lett.

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The intensively studied Si(111)-(5 Â 2)-Au surface is reexamined using reflectance anisotropy spectroscopy and density functional theory simulations. We identify distinctive spectral features relating directly to local structural motifs such as Si honeycomb chains and atomic gold wires that are commonly found on Au-reconstructed vicinal Si(111) surfaces. Optical signatures of chain dimerization, responsible for the observed (Â 2) periodicity, are identified. The optical response, together with STM simulations and first-principles total-energy calculations, exclude the new structure proposed very recently based on the reflection high-energy electron diffraction technique analysis of Abukawa and Nishigaya [Phys. Rev. Lett. 110, 036102 (2013)] and provide strong support for the Si honeycomb chain with the triple Au chain model of Erwin et al. [Phys. Rev. B 80, 155409 (2009)]. This is a promising approach for screening possible models of complex anisotropic surface structures. DOI: 10.1103/PhysRevLett.111.087401 PACS numbers: 78.68.+m, 73.20.Àr, 78.20.Bh The Si(111)-(5 Â 2)-Au surface has been the subject of long and intensive experimental and theoretical study, due to its potential for applications in nanoelectronics and its prototypical nature for studying self-assembly and properties of one-dimensional quantum structures [1,2]. On the experimental side, this includes STM [3][4][5], reflection high-energy electron diffraction (RHEED) [6], LEED [7], photoemission [8][9][10], and optical spectroscopy [11,12]; theoretical works generally focus on surface energies, electronic structure, and STM simulations [13][14][15][16]. Nonetheless, its structure remains controversial. Significant inconsistencies arose when even the most promising structures, all of which feature a Si honeycomb chain [17], were compared with experimental data [5].The recalibration in 2009 [18] of the Au coverage from 0.4 monolayers (ML) to 0.6 ML prompted a reevaluation of the Si(111)-(5Â2)-Au atomic structure. In particular, an exhaustive theoretical-experimental study by Erwin-Barke-Himpsel [16] (henceforth, EBH) proposed a three-chain model that largely resolved the remaining discrepancies in the STM and photoemission data [5]. However, a recent RHEED study by Abukawa and Nishigaya [6] (henceforth, AN) predicted a completely new structure, which appears consistent with Y-shaped structures found in STM [3,5]. Most notably, the model does not contain Si honeycomb chains.Independent evaluation of competing structural models is provided by reflectance anisotropy spectroscopy (RAS) [19]. The technique probes both filled and empty surface and interface states while discriminating against the bulk response of cubic materials and hence is particularly sensitive to the local surface and interface atomic structure. Moreover, RAS simulation has now evolved to a level capable of producing impressive agreement with experiment, revealing sensitivity to subtle structural phenomena, such as dimer composition [20] [26] in interface systems. Adsorbaterecon...

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Evolutionary approach for finding the atomic structure of steps on stable crystal surfaces

Cited by 19 publications

References 34 publications

Systematic investigation of the structure of the Si(553)-Au surface from first principles

Systematic investigation of the structure of the Si(553)-Au surface from first principles

Evolutionary method for predicting surface reconstructions with variable stoichiometry

Optical Fingerprints of Si Honeycomb Chains and Atomic Gold Wires on the Si(111)-(5×2)-Au Surface

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