scholarly journals Methanol Adsorption on Graphene

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Elsebeth Schröder
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
First Principles ◽  
Density Functional ◽  
Dispersion Interactions ◽  
High Coverage ◽  
Methanol Adsorption ◽  
Polycyclic Aromatic ◽  
Adsorption Energies ◽  
Good Agreement

The adsorption energies and orientation of methanol on graphene are determined from first-principles density functional calculations. We employ the well-tested vdW-DF method that seamlessly includes dispersion interactions with all of the more close-ranged interactions that result in bonds like the covalent and hydrogen bonds. The adsorption of a single methanol molecule and small methanol clusters on graphene is studied at various coverages. Adsorption in clusters or at high coverages (less than a monolayer) is found to be preferable, with the methanol C-O axis approximately parallel to the plane of graphene. The adsorption energies calculated with vdW-DF are compared with previous DFT-D and MP2-based calculations for single methanol adsorption on flakes of graphene (polycyclic aromatic hydrocarbons). For the high coverage adsorption energies, we also find reasonably good agreement with previous desorption measurements.

scholarly journals High-pressure elastic properties of polycyclic aromatic hydrocarbons obtained by first-principles calculations

2019 ◽  
Vol 64 (5) ◽  
pp. 460-470
Author(s):  
K. D. Litasov ◽  
T. M. Inerbaev ◽  
F. U. Abuova ◽  
A. D. Chanyshev ◽  
A. K. Dauletbekova ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
First Principles ◽  
Density Functional ◽  
Pressure Derivative ◽  
Benzene Rings ◽  
Polycyclic Aromatic ◽  
Intermolecular Distances

Crystal structure and compressibility parameters of benzene and a number of polycyclic aromatic hydrocarbons (PAHs) were calculated by first-principles methods of the density functional theory with a gradient approximation of the exchange-correlation potential in the form of PBE, taking into account the van der Waals interactions optPBE-vdW in a pressure interval of 0–20 GPa. A comparison with the experimental data for benzene, naphthalene, tetracene, and pentacene shows a high accuracy of the calculations. All studied materials have a close compressibility with the bulk modulus from 8 to 12 GPa and its pressure derivative 6.9–7.5, which consistent with a decrease in the intermolecular distances and a weak deformation of the molecules and benzene rings themselves. There is a weak dependence of the compressibility on the number of atoms (benzene rings) in the molecule or on the type of crystal structure (most PAHs have a space group P 21/a). Compounds with a large number of benzene rings, as well as a denser ring structure – cyclic (pyrene, coronene) have lower compressibility with respect to less dense PAHs (tetracene, hexacene). Some PAHs, benzene, phenanthrene, pyrene and coronene, have high-pressure modifications, but a correct description of their structures, which allows to obtain elastic modules, has not yet been made. The obtained data on PAH compressibility can be used in the development of high-temperature equations of state and calculation of the equilibrium composition of the liquid and solid components of the C-O-H system.

scholarly journals Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons

Chemistry ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 532-549
Author(s):  
Felix Plasser
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Excited States ◽  
Aromatic Hydrocarbons ◽  
Density Functional ◽  
Materials Science ◽  
Chemical Shifts ◽  
Qualitative Description ◽  
Triplet States ◽  
Excitation Energies ◽  
Polycyclic Aromatic

Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four biphenylene-derived PAHs finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). The results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states.

scholarly journals Exploitation of Baird Aromaticity and Clar's Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons

2021 ◽  
Author(s):  
Felix Plasser
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Excited States ◽  
Aromatic Hydrocarbons ◽  
Density Functional ◽  
Materials Science ◽  
Chemical Shifts ◽  
Qualitative Description ◽  
Triplet States ◽  
Excitation Energies ◽  
Polycyclic Aromatic

Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four PAHs based on the biphenylene motif finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). These results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states.

scholarly journals A topological model for predicting adsorption energies of polycyclic aromatic hydrocarbons on late-transition metal surfaces

2019 ◽  
Vol 4 (2) ◽  
pp. 410-417
Author(s):  
Zhao-Bin Ding ◽  
Matteo Tommasini ◽  
Matteo Maestri
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Transition Metal ◽  
Aromatic Hydrocarbons ◽  
Topological Model ◽  
Late Transition Metal ◽  
Formation Enthalpies ◽  
Transition Metal Surfaces ◽  
Polycyclic Aromatic ◽  
Adsorption Energies ◽  
Late Transition

A topological model for the adsorption of PAHs is derived based on an analogy with the formation enthalpies of metal complexes.

Computational Study of the Effect of Dispersion Interactions on the Thermochemistry of Aggregation of Fused Polycyclic Aromatic Hydrocarbons as Model Asphaltene Compounds in Solution

2014 ◽  
Vol 118 (5) ◽  
pp. 896-908 ◽  
Author(s):  
Leonardo Moreira da Costa ◽  
Stanislav R. Stoyanov ◽  
Sergey Gusarov ◽  
Peter R. Seidl ◽  
José Walkimar de M. Carneiro ◽  
...  
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Computational Study ◽  
Dispersion Interactions ◽  
Polycyclic Aromatic

Hydrogenated polycyclic aromatic hydrocarbons (HnPAHs) as catalysts for hydrogenation reactions in the interstellar medium: a quantum chemical model

2019 ◽  
Vol 21 (22) ◽  
pp. 12012-12020 ◽  
Author(s):  
Ricardo M. Ferullo ◽  
Carolina E. Zubieta ◽  
Patricia G. Belelli
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Quantum Chemical ◽  
Density Functional ◽  
Activation Barrier ◽  
Functional Studies ◽  
Quantum Chemical Model ◽  
Polycyclic Aromatic ◽  
Hydrogenation Reactions ◽  
No Activation

Density functional studies show that neutral HnPAHs are able to catalyze the formation of water with no activation barrier.

scholarly journals Estimation of n-octanol/water partition coefficients of polycyclic aromatic hydrocarbons by quantum chemical descriptors

2008 ◽  
Vol 6 (2) ◽  
pp. 310-318 ◽  
Author(s):  
Gui-Ning Lu ◽  
Xue-Qin Tao ◽  
Zhi Dang ◽  
Xiao-Yun Yi ◽  
Chen Yang
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Aromatic Hydrocarbons ◽  
Quantum Chemical ◽  
Partition Coefficients ◽  
Density Functional ◽  
Optimal Model ◽  
Quantum Chemical Descriptors ◽  
Polycyclic Aromatic ◽  
Pls Analysis ◽  
Chemical Descriptors

AbstractQuantitative structure-property relationship (QSPR) modeling is a powerful approach for predicting environmental behavior of organic pollutants with their structure descriptors. This study reports an optimal QSPR model for estimating logarithmic n-octanol/water partition coefficients (log K OW) of polycyclic aromatic hydrocarbons (PAHs). Quantum chemical descriptors computed with density functional theory at B3LYP/6-31G(d) level and partial least squares (PLS) analysis with optimizing procedure were used for generating QSPR models for log K OW of PAHs. The squared correlation coefficient (R 2) of the optimal model was 0.990, and the results of crossvalidation test (Q 2cum=0.976) showed this optimal model had high fitting precision and good predictability. The log K OW values predicted by the optimal model are very close to those observed. The PLS analysis indicated that PAHs with larger electronic spatial extent and lower total energy values tend to be more hydrophobic and lipophilic.

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