Multiscale modeling and simulation (MMS) combining B97-D/TZV2P DFT calculations molecular dynamics simulations are performed to investigate the adsorption of hydrogen over coronene as a model graphene.

High-level quantum-chemical methods show that the binding in inclusion complex of hexamethylbenzene (HMB) 6-cycloparaphenilacetylene (6-CPPA) cannot be explained only terms electrostatic interactions-caused by polarization associated to curved pi-conjugated systems-and dispersion forces is definitely needed. The theoretical description van der Waals interactions notoriously complicated and fact some DFT even predict existence relatively small supramolecular nanoring studied here. However, ab...

Decomposing the Hartree-Fock one-electron density matrix and a virtual pseudodensity matrix, we obtain an orthogonal set of normalized molecular orbitals with local character to be used in post-Hartree-Fock calculations. The applicability procedure is illustrated by calculating CCSD(T) energies CCSD properties reduced active spaces.

Different force fields for the graphene–CH₄ system are proposed including pseudo-atom and full atomistic models.

The interaction of CO with graphene was studied at different theoretical levels. Quantum-mechanical calculations on finite models the use coronene for coupled cluster and circumcoronene B97D showed that there no preferential site adsorption most important factor orientation relative to graphene. parallel preferred, binding energies around 9 kJ mol-1 CCSD(T) levels, which in good agreement experimental findings. From a large number CO-circumcoronene CO-CO interactions, computed distances...

We theoretically investigate graphene layers, proposing them as membranes of subnanometer size suitable for CH4/N2 separation and gas uptake. The observed potential energy surfaces, representing the intermolecular interactions within gaseous mixtures between these have been formulated by adopting so-called Improved Lennard-Jones (ILJ) potential, which is far more accurate than traditional potential. Previously derived ILJ force fields are used to perform extensive molecular dynamics...

Despite being considered completely rigid in most studies, graphene is really flexible leading to out-of-plane movements. In this work, the influence of such flexibility on adsorption methane and nitrogen studied using molecular dynamics. Indeed, we have used intramolecular force fields for with in-plane components that allow describing movements deformations sheets providing a more realistic description adsorbent. addition, intermolecular validated at CCSD(T) level are used. We show...

We use large-scale MP2 calculations to investigate the physisorption of molecular hydrogen on (9,0) defective carbon nanotubes (CNTs) C72H18. These large (supra)molecular systems are typically studied using conventional DFT methods, which do not describe well van der Waals interactions responsible for this process. Here we CCSD(T)-calibrated estimate binding energies by considering four structures (hydrogenated divacancy, octagon-pentagon, and two Stone-Wales defects). The largest...

A new implementation of the approximate coupled cluster singles and doubles CC2 linear response model is reported. It employs a Cholesky decomposition two-electron integrals that significantly reduces computational cost storage requirements method compared to standard implementations. Our algorithm also exploits partitioning form equations which dimension problem avoids amplitudes. We present calculation excitation energies benzene using hierarchy basis sets compare results with conventional...

Using triples-corrected coupled-cluster methods as well other high-level theoretical approximations, the optimized parameters and isomerization barriers of family compounds cyclopentadiene-(benzene)x-cyclopentadiene (x = 0, 1, 2) are computed. In contrast to previous studies, s-indacene presents a localized C(2h) geometry. Also, structure pentalene is found be most stable, but when two benzene rings intercalated between five-member pentalene, resulting molecule preferably adopts delocalized...

Using correlated ab initio methods, the polarizability of large [4n + 2]-annulenes is determined, showing that there exists an almost linear relation between exaltation magnetic susceptibility (a measure aromaticity) and equivalent enlargement polarizability.

We use large-scale MP2 calculations to analyze the interactions appearing in amyloid fibers, which are difficult determine experimentally. To this end, dimers and trimers of hexapeptide NNQQNY from yeast prion-like protein Sup35 were considered as model systems. studied energy present three levels organization formation fibrils is structured. The structural changes hydrogen bonds too. It was found that most energetic process β-sheet, equally due both van der Waals interactions. aromatic...

Magnetic susceptibility and nuclear magnetic shielding at the nuclei of bis-heteropentalenes formed by two pyrrole units ([2,3−b], [3,2−b], [3,4−b], [3,4−c] isomers) have been evaluated a series different approximations large Gaussian basis set. An ab initio model field induced current density was obtained for four isomeric systems, showing that strong diamagnetic flow takes place within π electrons. The currents are responsible exalted anisotropy proton deshielding. theoretical findings...

The adsorption-for separation, storage and transportation-of methane, hydrogen their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising such an application, yet good design better understanding of the optimal pore size needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard-Jones potentials, are performed determine ideal interlayer distance slit-shaped graphene large...

Gauge origin independent calculations of nuclear magnetic shielding tensors are carried out inside the formalism continuous transformation current density leading to formal annihilation its diamagnetic contribution (CTOCD-DZ). We employ unrelaxed linear response approach with a hierarchy different coupled cluster methods in order assess importance level approximation expansion. The basis set dependence computed constants is also analyzed series correlation consistent sets, aim designing...

Magnetic susceptibility and nuclear magnetic shielding at the nuclei of bis-heteropentalenes formed by two furan units ([2,3-b], [3,2-b], [3,4-b], [3,4-c] isomers) have been computed several approximated techniques a large Gaussian basis set to achieve near Hartree-Fock estimates. Ab initio models ring currents induced field normal molecular plane were obtained for three isomeric systems higher symmetry, showing that pi electrons give rise intense diamagnetic circulation. The are responsible...

Near Hartree–Fock values of the magnetic susceptibility and nuclear shielding bis-heteropentalenes consisting two thiophene units ([2,3-b], [3,2-b], [3,4-b], [3,4-c] isomers) have been estimated via computational schemes relying on continuous transformation origin current density within coupled approximation extended gaugeless Gaussian basis sets. The results are compared with those obtained London gauge-including orbitals. Maps streamlines modulus ring induced by a field normal to molecular...

Tetraazanaphthalenes are diatropic molecules, whose magnetic response to a field perpendicular the molecular plane closely resembles that of naphthalene. The out-of-plane component susceptibility tensor and its strong anisotropy can be used as quantifiers aromaticity. Maps showing streamlines modulus current density provide clear evidence for diatropicity these systems. They also explain carbon nitrogen shielding, which is determined by big nuclear shielding tensor. electronic ring currents...

Chiral discrimination by nuclear magnetic resonance (NMR) spectroscopy might be achieved through the pseudo-scalar derived from dipole shielding polarizability tensor. Coupled Cluster Singles and Doubles-Quadratic Response (CCSD-QR) calculations inside continuous translation of origin current density formalism have been carried out to determine effects basis set, electron correlation, gauge on determination this magnitude in oxaziridine derivatives. Inclusion electronic correlation is needed...