Kinetic effects on the cycloaddition of 1,3-cyclohexadiene to the 3C-SiC(001)-3 × 2 surface studied via ab initio molecular dynamics

Robin L. Hayes, Mark Tuckerman

Research output: Contribution to journalArticle

Abstract

Silicon carbide (SiC) surfaces are often the semiconductor material of choice for applications under extreme conditions or with biocompatibility requirements. The SiC(001)-3 × 2 surface has a top Si tilted dimer that should react with π bonds in organic molecules, potentially forming a well-ordered semiconductor-organic interface. Ab initio molecular dynamics simulations of a prototype cycloaddition system, 1,3-cyclohexadiene (CHD) + SiC(001)-3 × 2, reveal that four products form via a two-step carbocation mechanism: [4 + 2] intradimer adduct, [2 + 2] intradimer adduct, H abstraction, and [4 + 2] subdimer adduct. The longer distance between dimers eliminates interdimer adducts that form on the Si(100)-2 × 1 system. CHD can wander more than 100 Å or 20 ps before finding the proper reactive environment. The intermediate lifetime ranges from 50 fs, when CHD is perfectly oriented, to more than 18 ps, when the CHD repeatedly visits the unstable [2 + 2] subdimer adduct. The reorientation caused by the [2 + 2] subdimer adduct favors hydrogen abstraction. Unfortunately, the [4 + 2] subdimer adduct destroys the reconstruction by creating an unsaturated Si in the third layer, thereby preventing cycloaddition reactions from creating a well-defined hybrid interface on this surface.

Original languageEnglish (US)
Pages (from-to)5880-5887
Number of pages8
JournalJournal of Physical Chemistry C
Volume112
Issue number15
DOIs
StatePublished - Apr 17 2008

Fingerprint

Cycloaddition
cycloaddition
Silicon carbide
silicon carbides
adducts
Molecular dynamics
molecular dynamics
Dimers
Kinetics
kinetics
Semiconducting organic compounds
Biocompatibility
Hydrogen
Semiconductor materials
dimers
Molecules
Computer simulation
organic semiconductors
biocompatibility
1,4-cyclohexadiene

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

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title = "Kinetic effects on the cycloaddition of 1,3-cyclohexadiene to the 3C-SiC(001)-3 × 2 surface studied via ab initio molecular dynamics",
abstract = "Silicon carbide (SiC) surfaces are often the semiconductor material of choice for applications under extreme conditions or with biocompatibility requirements. The SiC(001)-3 × 2 surface has a top Si tilted dimer that should react with π bonds in organic molecules, potentially forming a well-ordered semiconductor-organic interface. Ab initio molecular dynamics simulations of a prototype cycloaddition system, 1,3-cyclohexadiene (CHD) + SiC(001)-3 × 2, reveal that four products form via a two-step carbocation mechanism: [4 + 2] intradimer adduct, [2 + 2] intradimer adduct, H abstraction, and [4 + 2] subdimer adduct. The longer distance between dimers eliminates interdimer adducts that form on the Si(100)-2 × 1 system. CHD can wander more than 100 {\AA} or 20 ps before finding the proper reactive environment. The intermediate lifetime ranges from 50 fs, when CHD is perfectly oriented, to more than 18 ps, when the CHD repeatedly visits the unstable [2 + 2] subdimer adduct. The reorientation caused by the [2 + 2] subdimer adduct favors hydrogen abstraction. Unfortunately, the [4 + 2] subdimer adduct destroys the reconstruction by creating an unsaturated Si in the third layer, thereby preventing cycloaddition reactions from creating a well-defined hybrid interface on this surface.",
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N2 - Silicon carbide (SiC) surfaces are often the semiconductor material of choice for applications under extreme conditions or with biocompatibility requirements. The SiC(001)-3 × 2 surface has a top Si tilted dimer that should react with π bonds in organic molecules, potentially forming a well-ordered semiconductor-organic interface. Ab initio molecular dynamics simulations of a prototype cycloaddition system, 1,3-cyclohexadiene (CHD) + SiC(001)-3 × 2, reveal that four products form via a two-step carbocation mechanism: [4 + 2] intradimer adduct, [2 + 2] intradimer adduct, H abstraction, and [4 + 2] subdimer adduct. The longer distance between dimers eliminates interdimer adducts that form on the Si(100)-2 × 1 system. CHD can wander more than 100 Å or 20 ps before finding the proper reactive environment. The intermediate lifetime ranges from 50 fs, when CHD is perfectly oriented, to more than 18 ps, when the CHD repeatedly visits the unstable [2 + 2] subdimer adduct. The reorientation caused by the [2 + 2] subdimer adduct favors hydrogen abstraction. Unfortunately, the [4 + 2] subdimer adduct destroys the reconstruction by creating an unsaturated Si in the third layer, thereby preventing cycloaddition reactions from creating a well-defined hybrid interface on this surface.

AB - Silicon carbide (SiC) surfaces are often the semiconductor material of choice for applications under extreme conditions or with biocompatibility requirements. The SiC(001)-3 × 2 surface has a top Si tilted dimer that should react with π bonds in organic molecules, potentially forming a well-ordered semiconductor-organic interface. Ab initio molecular dynamics simulations of a prototype cycloaddition system, 1,3-cyclohexadiene (CHD) + SiC(001)-3 × 2, reveal that four products form via a two-step carbocation mechanism: [4 + 2] intradimer adduct, [2 + 2] intradimer adduct, H abstraction, and [4 + 2] subdimer adduct. The longer distance between dimers eliminates interdimer adducts that form on the Si(100)-2 × 1 system. CHD can wander more than 100 Å or 20 ps before finding the proper reactive environment. The intermediate lifetime ranges from 50 fs, when CHD is perfectly oriented, to more than 18 ps, when the CHD repeatedly visits the unstable [2 + 2] subdimer adduct. The reorientation caused by the [2 + 2] subdimer adduct favors hydrogen abstraction. Unfortunately, the [4 + 2] subdimer adduct destroys the reconstruction by creating an unsaturated Si in the third layer, thereby preventing cycloaddition reactions from creating a well-defined hybrid interface on this surface.

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