scholarly journals Simultaneous Suppression of pi- and sigma- Transmission in pi-Conjugated Molecules

2020 ◽  
Author(s):  
Marc Hamilton Garner ◽  
Gemma C. Solomon
Keyword(s):  
Density Functional ◽  
Structural Changes ◽  
Twist Angle ◽  
Dielectric Materials ◽  
Methyl Groups ◽  
Conjugated Molecules ◽  
Functional Theory ◽  
Pi Conjugated ◽  
Phenyl Rings ◽  
Open Question

<div><div><div><p>Molecular dielectric materials require ostensibly conflicting requirements of high polarizability and low conductivity. As previous efforts towards molecular insulators focused on saturated molecules, it remains an open question whether pi- and sigma-transport can be simultaneously suppressed in conjugated systems. Here, we demonstrate that there are conjugated molecules where the sigma-transmission is suppressed by destructive sigma-interference, while the pi-transmission can be suppressed by a localized disruption of conjugation. Using density functional theory, we study the Landauer transmission and ballistic current density, which allow us to determine how the transmission is affected by various structural changes in the molecule. We find that in para-linked oligophenyl rings the sigma-transmission can be suppressed by changing the remaining hydrogens to methyl groups due to the inherent gauche-like structure of the carbon backbone within a benzene ring, similar to what was previously seen in saturated systems. At the same time, the methyl groups fulfil a dual purpose as they modulate the twist angle between neighboring phenyl rings. When neighboring rings are orthogonal to each other, the transmission through both pi- and sigma-systems is effectively suppressed. Alternatively, breaking conjugation in a single phenyl ring by saturating two carbons atoms with two methyl substituents on each carbon, results in suppressed pi- and sigma-transport independent of dihedral angle. These two strategies demonstrate that methyl-substituted oligophenyls are promising candidates for the development of molecular dielectric materials.</p></div></div></div>

scholarly journals Simultaneous Suppression of pi- and sigma- Transmission in pi-Conjugated Molecules

2020 ◽  
Author(s):  
Marc Hamilton Garner ◽  
Gemma C. Solomon
Keyword(s):  
Density Functional ◽  
Structural Changes ◽  
Twist Angle ◽  
Dielectric Materials ◽  
Methyl Groups ◽  
Conjugated Molecules ◽  
Functional Theory ◽  
Pi Conjugated ◽  
Phenyl Rings ◽  
Open Question

<div><div><div><p>Molecular dielectric materials require ostensibly conflicting requirements of high polarizability and low conductivity. As previous efforts towards molecular insulators focused on saturated molecules, it remains an open question whether pi- and sigma-transport can be simultaneously suppressed in conjugated systems. Here, we demonstrate that there are conjugated molecules where the sigma-transmission is suppressed by destructive sigma-interference, while the pi-transmission can be suppressed by a localized disruption of conjugation. Using density functional theory, we study the Landauer transmission and ballistic current density, which allow us to determine how the transmission is affected by various structural changes in the molecule. We find that in para-linked oligophenyl rings the sigma-transmission can be suppressed by changing the remaining hydrogens to methyl groups due to the inherent gauche-like structure of the carbon backbone within a benzene ring, similar to what was previously seen in saturated systems. At the same time, the methyl groups fulfil a dual purpose as they modulate the twist angle between neighboring phenyl rings. When neighboring rings are orthogonal to each other, the transmission through both pi- and sigma-systems is effectively suppressed. Alternatively, breaking conjugation in a single phenyl ring by saturating two carbons atoms with two methyl substituents on each carbon, results in suppressed pi- and sigma-transport independent of dihedral angle. These two strategies demonstrate that methyl-substituted oligophenyls are promising candidates for the development of molecular dielectric materials.</p></div></div></div>

scholarly journals Simultaneous Suppression of pi- and sigma- Transmission in pi-Conjugated Molecules

2020 ◽  
Author(s):  
Marc Hamilton Garner ◽  
Gemma C. Solomon
Keyword(s):  
Density Functional ◽  
Structural Changes ◽  
Twist Angle ◽  
Dielectric Materials ◽  
Methyl Groups ◽  
Conjugated Molecules ◽  
Functional Theory ◽  
Pi Conjugated ◽  
Phenyl Rings ◽  
Open Question

<div><div><div><p>Molecular dielectric materials require ostensibly conflicting requirements of high polarizability and low conductivity. As previous efforts towards molecular insulators focused on saturated molecules, it remains an open question whether pi- and sigma-transport can be simultaneously suppressed in conjugated systems. Here, we demonstrate that there are conjugated molecules where the sigma-transmission is suppressed by destructive sigma-interference, while the pi-transmission can be suppressed by a localized disruption of conjugation. Using density functional theory, we study the Landauer transmission and ballistic current density, which allow us to determine how the transmission is affected by various structural changes in the molecule. We find that in para-linked oligophenyl rings the sigma-transmission can be suppressed by changing the remaining hydrogens to methyl groups due to the inherent gauche-like structure of the carbon backbone within a benzene ring, similar to what was previously seen in saturated systems. At the same time, the methyl groups fulfil a dual purpose as they modulate the twist angle between neighboring phenyl rings. When neighboring rings are orthogonal to each other, the transmission through both pi- and sigma-systems is effectively suppressed. Alternatively, breaking conjugation in a single phenyl ring by saturating two carbons atoms with two methyl substituents on each carbon, results in suppressed pi- and sigma-transport independent of dihedral angle. These two strategies demonstrate that methyl-substituted oligophenyls are promising candidates for the development of molecular dielectric materials.</p></div></div></div>

Suppression of the Sigma-Transmission by Destructive Quantum Interference in Pi-Conjugated Molecules

2020 ◽  
Author(s):  
Marc Hamilton Garner ◽  
Gemma C. Solomon
Keyword(s):  
Quantum Interference ◽  
Density Functional ◽  
Structural Changes ◽  
Dielectric Materials ◽  
Conjugated Molecules ◽  
Functional Theory ◽  
Conjugated Systems ◽  
Pi Conjugated ◽  
Phenyl Rings ◽  
Open Question

<div><div><div><p>Molecular dielectric materials require ostensibly conflicting requirements of high polarizability and low conductivity. As previous efforts towards molecular insulators focused on saturated molecules, where the polarizability will be generally less than conjugated molecules, it remains an open question whether electron transport can be comprehensively suppressed in conjugated systems. Here, we demonstrate that the s-transmission in conjugated oligophenyl</p><p>systems can be suppressed by destructive sigma-interference. Using density functional theory, we study the Landauer transmission and ballistic current density, which allow us to determine how the transmission is affected by structural changes in the molecule. In para-linked phenyl rings, the sigma- transmission can be suppressed by changing the remaining hydrogens to methyl substituents due to the inherent gauche-like structure of a benzene ring. When two neighboring phenyl rings are orthogonal to each other, the transmission through both pi- and sigma-systems can be effectively suppressed, making methyl-substituted oligophenyls promising candidates for conjugated insulators.</p></div></div></div>

scholarly journals Effect of π-conjugated molecules on electronics properties of benzene-diamine derivatives

2021 ◽  
Vol 19 (50) ◽  
pp. 70-76
Author(s):  
Mohsin Al-Khaykanee ◽  
Ali Al-Jawdahb
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Conjugated Molecules ◽  
Functional Theory ◽  
Pi Conjugated ◽  
Phenyl Rings ◽  
Mechanical Approach ◽  
Quantum Mechanical Approach ◽  
Chemical Groups ◽  
Theoretical Results

The present work shows a theoretical results that have been used the functional Hybrid of three parameters Lee-Yang-Parr (B3LYP) of the quantum mechanical approach for density functional theory with (Spanish Initiative for Electronic Simulations with Thousands of Atoms) SIESTA code. All calculations were carried out employing the used method at the Gaussian 09 package of programs. It was reported the main point for research on dominance of the bandgap of elongated pi-conjugated molecules by using different chemical groups replacing hydrogen atom in the most molecules that used in this work. The side groups creates another factor that controls the value of the band gap. The dihedral angle between the two phenyl rings plays more important role in controlling the band gap in these molecules.

scholarly journals Defect Processes in Halogen Doped SnO2

2021 ◽  
Vol 11 (2) ◽  
pp. 551
Author(s):  
Petros-Panagis Filippatos ◽  
Nikolaos Kelaidis ◽  
Maria Vasilopoulou ◽  
Dimitris Davazoglou ◽  
Alexander Chroneos
Keyword(s):  
Electronic Properties ◽  
Tin Oxide ◽  
Density Functional ◽  
Structural Changes ◽  
High Dielectric Constant ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Optical And Electronic Properties ◽  
High Dielectric ◽  
Gap States

In the present study, we performed density functional theory calculations (DFT) to investigate structural changes and their impact on the electronic properties in halogen (F, Cl, Br, and I) doped tin oxide (SnO2). We performed calculations for atoms intercalated either at interstitial or substitutional positions and then calculated the electronic structure and the optical properties of the doped SnO2. In all cases, a reduction in the bandgap value was evident, while gap states were also formed. Furthermore, when we insert these dopants in interstitial and substitutional positions, they all constitute a single acceptor and donor, respectively. This can also be seen in the density of states through the formation of gap states just above the valence band or below the conduction band, respectively. These gap states may contribute to significant changes in the optical and electronic properties of SnO2, thus affecting the metal oxide’s suitability for photovoltaics and photocatalytic devices. In particular, we found that iodine (I) doping of SnO2 induces a high dielectric constant while also reducing the oxide’s bandgap, making it more efficient for light-harvesting applications.

scholarly journals Effect of chemical modification on electronic transport properties of carbyne

2021 ◽  
Author(s):  
G. R. Berdiyorov ◽  
U. Khalilov ◽  
H. Hamoudi ◽  
Erik C. Neyts
Keyword(s):  
Transport Properties ◽  
Electronic Transport ◽  
Density Functional ◽  
Structural Changes ◽  
Carbon Chain ◽  
Functional Formalism ◽  
Functional Theory ◽  
Carbon Allotrope ◽  
Electronic Transport Properties ◽  
Interface Structures

AbstractUsing density functional theory in combination with the Green’s functional formalism, we study the effect of surface functionalization on the electronic transport properties of 1D carbon allotrope—carbyne. We found that both hydrogenation and fluorination result in structural changes and semiconducting to metallic transition. Consequently, the current in the functionalization systems increases significantly due to strong delocalization of electronic states along the carbon chain. We also study the electronic transport in partially hydrogenated carbyne and interface structures consisting of pristine and functionalized carbyne. In the latter case, current rectification is obtained in the system with rectification ratio up to 50%. These findings can be useful for developing carbyne-based structures with tunable electronic transport properties.

scholarly journals Structural and computational investigation of an imine-based propeller-shaped macrocyclic cage

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Sriram Srinivasa Raghvan ◽  
Suresh Madhu ◽  
Velmurugan Devadasan ◽  
Gunasekaran Krishnasamy
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Strain Tensor ◽  
Strong Interactions ◽  
Soft Condensed Matter ◽  
Functional Theory ◽  
Self Assembling ◽  
Phenyl Rings ◽  
Crystal Volume

AbstractIn this study, we present the synthesis, spectroscopic and structural characterization of self-assembling gem-dimethyl imine based molecular cage (IMC). Self-assembling macrocycles and cages have well-defined cavities and have extensive functionalities ranging from energy storage, liquid crystals, and catalysts to water splitting photo absorber. IMC has large voids i.e., 25% of the total crystal volume thus could accommodate wide substrates. The synthesized imine-based molecular cages are stabilized by coaxial π bonded networks and long-range periodic van der Waal and non-bonded contacts as observed from the crystal structure. IMC also has typical properties of soft condensed matter materials, hence theoretical prediction of stress and strain tensor along with thermophysical properties were computed on crystal system and were found to be stable. Molecular dynamics revealed IMC is stabilized by, strong interactions between the interstitial phenyl rings. Density functional theory (DFT) based physicochemical properties were evaluated and has band gap of around 2.38ev (520 nm) similar to various photocatalytic band gap materials.

High modulus oxide glasses

2015 ◽  
Vol 2015 (CICMT) ◽  
pp. 000038-000040
Author(s):  
K. Philipps ◽  
R. P. Stoffel ◽  
R. Dronskowski ◽  
R. Conradt
Keyword(s):  
Short Range ◽  
Density Functional ◽  
Elastic Moduli ◽  
Structural Changes ◽  
Glassy Phase ◽  
Oxide Glasses ◽  
High Modulus ◽  
Functional Theory ◽  
Crystalline Phases ◽  
Glassy Materials

Elastic properties of glassy materials were studied in comparison to the isochemical crystalline phases. Structural changes were studied by density-functional theory with respect to electronic, vibrational, mechanical and thermodynamic properties. It turned out that topology is essential for elastic moduli. For both, glasses and crystals, elastic moduli are a function of atomic packing density, short range order, and especially the nature of the connection of adjacent polyhedra. Both, glassy and crystalline phases, behave in a commensurable way so that the glassy phase can be handled as a member of a series of polymorphs with the same stoichiometry.

scholarly journals Atomic-Scale Understanding of Structure and Properties of Complex Pyrophosphate Crystals by First-Principles Calculations

2019 ◽  
Vol 9 (5) ◽  
pp. 840 ◽  
Author(s):  
Redouane Khaoulaf ◽  
Puja Adhikari ◽  
Mohamed Harcharras ◽  
Khalid Brouzi ◽  
Hamid Ez-Zahraouy ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Atomic Scale ◽  
Functional Theory ◽  
Local Structures ◽  
Cationic Group ◽  
Metallic Cations ◽  
Bonding And Bridging ◽  
Open Question

The electronic structure and mechanical and optical properties of five pyrophosphate crystals with very complex structures are studied by first principles density functional theory calculations. The results show the complex interplay of the minor differences in specific local structures and compositions can result in large differences in reactivity and interaction that are rare in other classes of inorganic crystals. These are discussed by dividing the pyrophosphate crystals into three structural units. H2P2O7 is the most important and dominating unit in pyrophosphates. The other two are the influential cationic group with metals and water molecules. The strongest P-O bond in P2O5 is the strongest bond for crystal cohesion, but O-H and N-H bonds also play an important part. Different type of bonding between O and H atoms such as O-H, hydrogen bonding, and bridging bonds are present. Metallic cations such as Mg, Zn, and Cu form octahedral bonding with O. The water molecule provides the unique H∙∙∙O bonds, and metallic elements can influence the structure and bonding to a certain extent. The two Cu-containing phosphates show the presence of narrow metallic bands near the valence band edge. All this complex bonding affects their physical properties, indicating that fundamental understanding remains an open question.

EFFECTS OF SULFUR SUBSTITUTIONAL IMPURITIES ON ZnO STRUCTURE USING DENSITY FUNCTIONAL THEORY

2011 ◽  
Vol 10 (03) ◽  
pp. 381-390
Author(s):  
MANUEL ALBERTO FLORES-HIDALGO ◽  
DIANA BARRAZA-JIMÉNEZ ◽  
DANIEL GLOSSMAN-MITNIK
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Structural Changes ◽  
Theoretical Calculations ◽  
Plane Waves ◽  
Crystal Form ◽  
Functional Theory ◽  
Substitutional Impurity ◽  
Gap Energy ◽  
Other Substances

Zinc oxide ( ZnO ) electrical properties can be modified by addition of impurities or defects such as vacancies or other substances. We use sulfur ( S ) as a substitutional impurity and present a theoretical study on the characteristics of ZnO structures in its crystal form containing S in substitution of O . For theoretical calculations we used Density Functional Theory (DFT) with pseudopotentials and plane waves. ZnO in crystal form with S in substitution of O at heavy percentage was studied by analyzing properties like lattice characteristics, total energy, and gap energy. Lattice parameters a, b, c, and c/a ratio increase with the S -substituent percentage while the crystal stability decreases. Variation of gap energy shows a decreasing trend with increasing amount of substitution. In this paper, we provide a detailed data useful to identify the effects on ZnO in its crystal form when O is replaced by S that will help to predict if the structural changes on the modified ZnO structures may be suitable for applications in opto-electronics.

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