Non-Closed-Shell Linear Chain: TheH4nSystem

The one-dimensional carbon allotrope carbyne, a linear chain of sp-hybridized carbon atoms, is predicted to exist in a polyynic and a cumulenic structure. While molecular forms of carbyne have been extensively characterized, the structural nature is hard to determine for many linear carbon wires that are made in-situ during pulling experiments. Here, we show that cumulenes and polyynes have distinctively different low-bias conductance profiles under axial torsion. We analyze the change of the electronic structure, Landauer transmission, and ballistic current density of the three types of closed-shell molecular carbynes as a function of the torsion angle. Both polyynic, odd-carbon cumulenic, and even-carbon cumulenic carbon wires exhibit helical frontier molecular orbitals when the end-groups are not in a co-planar configuration. This helical conjugation effect gives rise to strong ring current patterns around the linear wires. Only the transmission of even-carbon polyynic wires follows the well-known cosine-squared law with axial torsion that is also seen in biphenyl-type systems. Notably, the transmission of even-carbon cumulenic carbon wires rises with axial torsion from co-planar towards perpendicular orientation of the end-groups. The three distinct transmission profiles of polyynes, odd-carbon cumulenes, and even-carbon cumulenes may allow for experimental identification of the structural nature of linear carbon wires. Their different electron transport properties under axial torsion furthermore underline that, in the molecular limit of carbyne, three different subclasses of linear carbon wires exist.

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Three Distinct Torsion Profiles of Electronic Transmission Through Linear Carbon Wires

10.26434/chemrxiv.11901894.v2 ◽

2020 ◽

Author(s):

Marc Hamilton Garner ◽

William Bro-Jørgensen ◽

Gemma C. Solomon

Keyword(s):

Linear Chain ◽

Type Systems ◽

Closed Shell ◽

Molecular Forms ◽

Carbon Allotrope ◽

Axial Torsion ◽

End Groups ◽

Structural Nature ◽

Electron Transport Properties ◽

The One

The one-dimensional carbon allotrope carbyne, a linear chain of sp-hybridized carbon atoms, is predicted to exist in a polyynic and a cumulenic structure. While molecular forms of carbyne have been extensively characterized, the structural nature is hard to determine for many linear carbon wires that are made in-situ during pulling experiments. Here, we show that cumulenes and polyynes have distinctively different low-bias conductance profiles under axial torsion. We analyze the change of the electronic structure, Landauer transmission, and ballistic current density of the three types of closed-shell molecular carbynes as a function of the torsion angle. Both polyynic, odd-carbon cumulenic, and even-carbon cumulenic carbon wires exhibit helical frontier molecular orbitals when the end-groups are not in a co-planar configuration. This helical conjugation effect gives rise to strong ring current patterns around the linear wires. Only the transmission of even-carbon polyynic wires follows the well-known cosine-squared law with axial torsion that is also seen in biphenyl-type systems. Notably, the transmission of even-carbon cumulenic carbon wires rises with axial torsion from co-planar towards perpendicular orientation of the end-groups. The three distinct transmission profiles of polyynes, odd-carbon cumulenes, and even-carbon cumulenes may allow for experimental identification of the structural nature of linear carbon wires. Their different electron transport properties under axial torsion furthermore underline that, in the molecular limit of carbyne, three different subclasses of linear carbon wires exist.

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THEORETICAL STUDY ON OPEN-SHELL NONLINEAR OPTICAL MOLECULAR SYSTEMS AND A DEVELOPMENT OF A NOVEL COMPUTATIONAL SCHEME OF EXCITON DYNAMICS

International Journal of Nanoscience ◽

10.1142/s0219581x09005803 ◽

2009 ◽

Vol 08 (01n02) ◽

pp. 123-129 ◽

Cited By ~ 1

Author(s):

MASAYOSHI NAKANO ◽

RYOHEI KISHI ◽

HITOSHI FUKUI ◽

TAKUYA MINAMI ◽

HIROSHI NAGAI ◽

...

Keyword(s):

Density Functional ◽

Nonlinear Optical ◽

Linear Chain ◽

Density Functional Theory Method ◽

Closed Shell ◽

Open Shell ◽

Quantum Master Equation ◽

Structure Property ◽

Electron Hole ◽

Molecular Systems

This contribution firstly elucidates a structure–property relationship in third-order nonlinear optical molecular systems with singlet diradical characters. It turns out that the second hyperpolarizabilities (γ) of the singlet open-shell molecules with intermediate diradical characters are significantly enhanced as compared with those of closed-shell and pure diradical molecules. The hybrid density functional theory method, i.e. UBHandHLYP, is applied to the calculations of γ of dimer models composed of singlet diradical diphenalenyl molecules, which show a remarkable enhancement of γ per monomer as decreasing the intermolecular distance. The second contribution is concerned with a development of ab initio molecular orbital configuration-interaction-based quantum master equation (QME) approach. This is found to provide both coherent processes, e.g. dynamic polarization and exciton (electron–hole pair) recurrence motion, and incoherent processes, e.g. exciton migration, in molecular systems. Using this approach, the electron/hole dynamics for dynamic polarizabilities α(ω) are examined for several π-conjugated linear chain systems, and the structural dependences of α(ω) are elucidated.

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Three Distinct Torsion Profiles of Electronic Transmission Through Linear Carbon Wires

10.26434/chemrxiv.11901894 ◽

2020 ◽

Author(s):

Marc Hamilton Garner ◽

William Bro-Jørgensen ◽

Gemma C. Solomon

Keyword(s):

Linear Chain ◽

Type Systems ◽

Closed Shell ◽

Molecular Forms ◽

Carbon Allotrope ◽

Axial Torsion ◽

End Groups ◽

Structural Nature ◽

Electron Transport Properties ◽

The One

The one-dimensional carbon allotrope carbyne, a linear chain of sp-hybridized carbon atoms, is predicted to exist in a polyynic and a cumulenic structure. While molecular forms of carbyne have been extensively characterized, the structural nature is hard to determine for many linear carbon wires that are made in-situ during pulling experiments. Here, we show that cumulenes and polyynes have distinctively different low-bias conductance profiles under axial torsion. We analyze the change of the electronic structure, Landauer transmission, and ballistic current density of the three types of closed-shell molecular carbynes as a function of the torsion angle. Both polyynic, odd-carbon cumulenic, and even-carbon cumulenic carbon wires exhibit helical frontier molecular orbitals when the end-groups are not in a co-planar configuration. This helical conjugation effect gives rise to strong ring current patterns around the linear wires. Only the transmission of even-carbon polyynic wires follows the well-known cosine-squared law with axial torsion that is also seen in biphenyl-type systems. Notably, the transmission of even-carbon cumulenic carbon wires rises with axial torsion from co-planar towards perpendicular orientation of the end-groups. The three distinct transmission profiles of polyynes, odd-carbon cumulenes, and even-carbon cumulenes may allow for experimental identification of the structural nature of linear carbon wires. Their different electron transport properties under axial torsion furthermore underline that, in the molecular limit of carbyne, three different subclasses of linear carbon wires exist.

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MAGNETIC AND CORRELATION EFFECTS IN A NON-CLOSED-SHELL LINEAR CHAIN

Le Journal de Physique Colloques ◽

10.1051/jphyscol:19711287 ◽

1971 ◽

Vol 32 (C1) ◽

pp. C1-814-C1-815

Author(s):

W. T. KWO

Keyword(s):

Linear Chain ◽

Closed Shell ◽

Correlation Effects

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Three Distinct Torsion Profiles of Electronic Transmission Through Linear Carbon Wires

10.26434/chemrxiv.11901894.v3 ◽

2020 ◽

Author(s):

Marc Hamilton Garner ◽

William Bro-Jørgensen ◽

Gemma C. Solomon

Keyword(s):

Linear Chain ◽

Type Systems ◽

Closed Shell ◽

Molecular Forms ◽

Carbon Allotrope ◽

Axial Torsion ◽

End Groups ◽

Structural Nature ◽

Electron Transport Properties ◽

The One

The one-dimensional carbon allotrope carbyne, a linear chain of sp-hybridized carbon atoms, is predicted to exist in a polyynic and a cumulenic structure. While molecular forms of carbyne have been extensively characterized, the structural nature is hard to determine for many linear carbon wires that are made in-situ during pulling experiments. Here, we show that cumulenes and polyynes have distinctively different low-bias conductance profiles under axial torsion. We analyze the change of the electronic structure, Landauer transmission, and ballistic current density of the three types of closed-shell molecular carbynes as a function of the torsion angle. Both polyynic, odd-carbon cumulenic, and even-carbon cumulenic carbon wires exhibit helical frontier molecular orbitals when the end-groups are not in a co-planar configuration. This helical conjugation effect gives rise to strong ring current patterns around the linear wires. Only the transmission of even-carbon polyynic wires follows the well-known cosine-squared law with axial torsion that is also seen in biphenyl-type systems. Notably, the transmission of even-carbon cumulenic carbon wires rises with axial torsion from co-planar towards perpendicular orientation of the end-groups. The three distinct transmission profiles of polyynes, odd-carbon cumulenes, and even-carbon cumulenes may allow for experimental identification of the structural nature of linear carbon wires. Their different electron transport properties under axial torsion furthermore underline that, in the molecular limit of carbyne, three different subclasses of linear carbon wires exist.

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Fractionation of polymethylene chains: An electron crystallographic investigation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100145315 ◽

1986 ◽

Vol 44 ◽

pp. 794-795

Author(s):

Douglas L. Dorset

Keyword(s):

Cross Section ◽

Binary Systems ◽

Linear Chain ◽

Pure Component ◽

Organic Substrates ◽

Crystallographic Investigation ◽

X Ray Diffraction ◽

X Ray ◽

Molecular Sizes ◽

The Stability

A variety of linear chain materials exist as polydisperse systems which are difficultly purified. The stability of continuous binary solid solutions assume that the Gibbs free energy of the solution is lower than that of either crystal component, a condition which includes such factors as relative molecular sizes and shapes and perhaps the symmetry of the pure component crystal structures.Although extensive studies of n-alkane miscibility have been carried out via powder X-ray diffraction of bulk samples we have begun to examine binary systems as single crystals, taking advantage of the well-known enhanced scattering cross section of matter for electrons and also the favorable projection of a paraffin crystal structure posited by epitaxial crystallization of such samples on organic substrates such as benzoic acid.

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Field ion microscope investigations of atomic processes at surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153117 ◽

1989 ◽

Vol 47 ◽

pp. 228-229

Author(s):

G. L. Kellogg ◽

P. R. Schwoebel

Keyword(s):

Single Crystal ◽

Crystal Surface ◽

Linear Chain ◽

Atom Probe ◽

Nucleation And Growth ◽

Single Atom ◽

Initial Structure ◽

Atomic Processes ◽

Single Crystal Surfaces ◽

Field Ion Microscope

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.

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