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Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation

The energy landscapes of ultra-thin nanofilms of ZnO and ZnS are examined in detail using periodic hybrid density functional calculations. We predict new staggered graphitic forms, which are stable only for the thinnest films and are of particular interest as the electronic structure shows a spontan...

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Autores principales: Conejeros, Sergio, Allan, Neil L., Claeyssens, Frederik, Hart, Judy N.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: RSC 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9419858/
https://www.ncbi.nlm.nih.gov/pubmed/36134212
http://dx.doi.org/10.1039/c8na00155c
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author Conejeros, Sergio
Allan, Neil L.
Claeyssens, Frederik
Hart, Judy N.
author_facet Conejeros, Sergio
Allan, Neil L.
Claeyssens, Frederik
Hart, Judy N.
author_sort Conejeros, Sergio
collection PubMed
description The energy landscapes of ultra-thin nanofilms of ZnO and ZnS are examined in detail using periodic hybrid density functional calculations. We predict new staggered graphitic forms, which are stable only for the thinnest films and are of particular interest as the electronic structure shows a spontaneous symmetry breaking across the film and consequently a marked decrease in band gap with thickness. The relative energies of the various forms, their structural and electronic properties and their variation with film thickness are discussed. Possible kinetic pathways for transitions from the graphitic forms are examined by explicit evaluation of transition state energies. For polar surfaces, such as (0001) würtzite and (111) zinc blende, many different mechanisms operate to remove or reduce the surface dipole depending on the number of layers in the nanofilm. The polar ZnS nanofilms, but not the polar ZnO analogues or any non-polar film, are predicted to spontaneously become non-stoichiometric by loss of zinc atoms from the surface. The behaviour of adsorbed water on the ultra-thin films is also examined. There is no dissociation on any ZnS film. For ZnO, dissociation into OH(−) and H(+) takes place not only on (101̄0) würtzite, but also on (110) zinc blende. This result that does not appear to have been reported previously and deserves future experimental study. While we concentrate on ZnO and ZnS, similar energy landscapes are expected for any oxide or sulphide which adopts the würtzite or zinc blende structure in the bulk.
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spelling pubmed-94198582022-09-20 Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation Conejeros, Sergio Allan, Neil L. Claeyssens, Frederik Hart, Judy N. Nanoscale Adv Chemistry The energy landscapes of ultra-thin nanofilms of ZnO and ZnS are examined in detail using periodic hybrid density functional calculations. We predict new staggered graphitic forms, which are stable only for the thinnest films and are of particular interest as the electronic structure shows a spontaneous symmetry breaking across the film and consequently a marked decrease in band gap with thickness. The relative energies of the various forms, their structural and electronic properties and their variation with film thickness are discussed. Possible kinetic pathways for transitions from the graphitic forms are examined by explicit evaluation of transition state energies. For polar surfaces, such as (0001) würtzite and (111) zinc blende, many different mechanisms operate to remove or reduce the surface dipole depending on the number of layers in the nanofilm. The polar ZnS nanofilms, but not the polar ZnO analogues or any non-polar film, are predicted to spontaneously become non-stoichiometric by loss of zinc atoms from the surface. The behaviour of adsorbed water on the ultra-thin films is also examined. There is no dissociation on any ZnS film. For ZnO, dissociation into OH(−) and H(+) takes place not only on (101̄0) würtzite, but also on (110) zinc blende. This result that does not appear to have been reported previously and deserves future experimental study. While we concentrate on ZnO and ZnS, similar energy landscapes are expected for any oxide or sulphide which adopts the würtzite or zinc blende structure in the bulk. RSC 2019-04-01 /pmc/articles/PMC9419858/ /pubmed/36134212 http://dx.doi.org/10.1039/c8na00155c Text en This journal is © The Royal Society of Chemistry https://creativecommons.org/licenses/by/3.0/
spellingShingle Chemistry
Conejeros, Sergio
Allan, Neil L.
Claeyssens, Frederik
Hart, Judy N.
Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation
title Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation
title_full Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation
title_fullStr Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation
title_full_unstemmed Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation
title_short Graphene and novel graphitic ZnO and ZnS nanofilms: the energy landscape, non-stoichiometry and water dissociation
title_sort graphene and novel graphitic zno and zns nanofilms: the energy landscape, non-stoichiometry and water dissociation
topic Chemistry
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9419858/
https://www.ncbi.nlm.nih.gov/pubmed/36134212
http://dx.doi.org/10.1039/c8na00155c
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AT claeyssensfrederik grapheneandnovelgraphiticznoandznsnanofilmstheenergylandscapenonstoichiometryandwaterdissociation
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