Density functional theory-based modeling of the half-metallic g-CN/CoN heterojunction for photocatalytic water splitting reaction.

Using density functional theory (DFT), we have investigated the structural, optical, electronic and magnetic properties of a graphitic carbon nitride (g-CN) and CoN composite to explore the effect of the heterojunction on the photocatalytic performance of g-CN. The structure of g-CN is modified while complexing with CoN and the corresponding stabilization is confirmed through adhesion energy calculation. The phonon spectra analysis furthermore guaranteed the lattice-dynamic stability of the CoN bulk and the CoN slab.

Comparative study of the photocatalytic activity of g-CN/MN (M = Mn, Fe, Co) for water splitting reaction: A theoretical study.

In this study, nanocomposites of g-CN/MN (where M is Mn, Fe and Co) have been designed using advanced density functional theory (DFT) calculations. A comprehensive analysis was conducted on the geometry, electronic, optical properties, work function, charge transfer interaction and adhesion energy of the g-CN/MN heterostructures and concluded that g-CN/FeN and g-CN/CoN heterojunctions exhibit higher photocatalytic performance than individual units. The better photocatalytic activity can be attributed mainly by two facts; (i) the visible light absorption of both g-CN/FeN and g-CN/CoN interfaces are higher compared to its isolated analogs and (ii) a significant enhancement of band gap energy in g-CN/FeN and g-CN/CoN heterostructures limited the electron-hole recombination significantly.

Calculation of salt-dependent free energy of binding of β-lactoglobulin homodimer formation and mechanism of dimer formation using molecular dynamics simulation and three-dimensional reference interaction site model (3D-RISM): diffuse salt ions and non-polar interactions between the monomers favor the dimer formation.

There are several important phenomena in chemistry, biology, and physics where molecules (or parts of a molecule) having charges of the same sign come closer together and become stable. DNA condensation, RNA folding, colloid-colloid interactions are some of the examples of this kind. In the current work, we have investigated how β-lactoglobulin, a protein found in milk, in spite of carrying +13 charge, favors the homodimer formation in the presence of salt.

Electrically controlled eight-spin-qubit entangled-state generation in a molecular break junction.

The generation of spin-based multi-qubit entangled states in the presence of an electric field is one of the most challenging tasks in current quantum-computing research. Such examples are still elusive. By using non-equilibrium Green's function-based quantum-transport calculations in combination with non-collinear spin density functional theory, we report that an eight-spin-qubit entangled state can be generated with the high-spin state of a dinuclear Fe(II) complex when the system is placed in a molecular break junction.

Chemical control of channel interference in two-photon absorption processes.

The two-photon absorption (TPA) process is the simplest and hence the most studied nonlinear optical phenomenon, and various aspects of this process have been explored in the past few decades, experimentally as well as theoretically. Previous investigations have shown that the two-photon (TP) activity of a molecular system can be tuned, and at present, performance-tailored TP active materials are easy to develop by monitoring factors such as length of conjugation, dimensionality of charge-transfer network, strength of donor-acceptor groups, polarity of solvents, self-aggregation, H-bonding, and micellar encapsulation to mention but a few. One of the most intriguing phenomena affecting the TP activity of a molecule is channel interference.

On the origin of the very strong two-photon activity of squaraine dyes--a standard/damped response theory study.

In the present work, we report the mechanism of a very large increase in the two-photon (TP) activity of squaraine based molecules upon changing the substituents. The replacement of a specific fused ring by ethylene or ethyne moieties enhances the TP transition strength of these molecules up to the order of 10(13) au (∼10(10) GM), both in the gas phase as well as in dichloromethane solvent. Our calculations decisively establish that the reason for this large enhancement in the TP activity of the studied systems is the severe decrease in the corresponding detuning energies.

Effect of donor-acceptor orientation on solvent-dependent three-photon activity in through-space charge-transfer systems--case study of [2,2]-paracyclophane derivatives.

We study the effect of donor-acceptor orientation on solvent-dependent three-photon transition probabilities (δ(3PA)) of representative through-space charge-transfer (TSCT) systems, namely, doubly positively charged [2,2]-paracyclophane derivatives. Our cubic response calculations reveal that the value of δ(3PA) may be as high as 10(6) a.u.

Electrostatic spin crossover and concomitant electrically operated spin switch action in a ti-based endohedral metallofullerene polymer.

Herein, we predict that a 1D chain of Ti@C(32) - C(2) - Ti@C(32) (TEMF) will act as a spin switch in the presence of an electric field. The spin resolved density of states analyses reveal that, surprisingly, both the low- and high-spin states of TEMF are half-metal; however, the metallic density of states comes from the opposite spin channels of the two spin states. More remarkably, it is found that the electric field driven spin crossover between the low and high state in TEMF is achievable at field strength 1.

On the origin of large two-photon activity of DANS molecule.

In this work, using the quadratic response theory and two-state model approach, we have explained the origin of high two-photon activity and the corresponding solvent dependence of 4,4'-dimethyl-amino-nitro-stilbene (DANS) molecule. For this purpose, we have made two structural modifications in the DANS molecule (1) at the donor-acceptor part and (2) at the unsaturated bridge between the two rings and calculated the one- and two-photon (OP and TP) absorption parameters of all the systems in gas phase and in three different solvents, viz., MeCN, THF, and toluene.

Enhancement of twist angle dependent two-photon activity through the proper alignment of ground to excited state and excited state dipole moment vectors.

Herein, we show that the two-photon (TP) transition probability (δTP) of o-betaine system will reach its maximum value at a twist angle around 65°. However, the potential energy scan with respect to the twist angle between its two rings indicates that the molecule in its ground state is quite unstable at this twist angle. Out of the different possibilities, the one having a single methyl group at the ortho position of the pyridinium ring is found to attain the optimum twist angle between the two rings, and interestingly, this particular substituted o-betaine has larger δTP value than any other substituted or pristine o-betaine.

On the microscopic origin of bending of graphene nanoribbons in the presence of a perpendicular electric field.

Herein, we predict that graphene nanoribbons will be nonplanar under the influence of a critical perpendicular field. Our investigation demonstrates that the perpendicular field induces mixing of σ and π orbitals in graphene nanoribbons through the second order Stark effect which eventually modulates the electron-nuclear interaction strongly in favor of a bent structure.

High-Polarity Solvents Decreasing the Two-Photon Transition Probability of Through-Space Charge-Transfer Systems - A Surprising In Silico Observation.

In the Letter, we address the question as to why larger two-photon absorption cross sections are observed in nonpolar than in polar solvents for through-space charge-transfer (TSCT) systems such as [2,2]-paracyclophane derivatives. In order to answer this question, we have performed ab initio calculations on two well-known TSCT systems, namely, a [2.2]-paracyclophane derivative and a molecular tweezer-trinitrofluorinone complex, and found that the two-photon transition probability values of these systems decreases with increasing solvent polarity.

The role of relativity and dispersion controlled inter-chain interaction on the band gap of thiophene, selenophene, and tellurophene oligomers.

Ab initio relativistic density functional theoretical calculations have been carried out on π-conjugated oligomers of increasing length with S, Se, and Te as heteroatoms. The band gap of the corresponding polymers has been obtained by plotting lowest unoccupied molecular orbital (LUMO)-highest occupied molecular orbital (HOMO)gap against the reciprocal of the number of monomer units (1/N) and extrapolating the curve to 1/N = 0. With B3LYP functional, we predict that role of relativistic correction terms is not very significant in the determination of final band gap of thiophene, selenophene, and tellurophene polymer.

Solvent induced channel interference in the two-photon absorption process--a theoretical study with a generalized few-state-model in three dimensions.

For the first time, we report the effect of interference between different optical channels on the two-photon absorption (TPA) process in three dimensions. We have employed response theory as well as a sum-over-states (SOS) approach involving few intermediate states to calculate the TPA parameters like transition probabilities (δ(TP)) and TPA tensor elements. In order to use the limited SOS approach, we have derived a new formula for a generalized few-state-model (GFSM) in three dimensions.

A critical theoretical study on the two-photon absorption properties of some selective triaryl borane-1-naphthylphenyl amine based charge transfer molecules.

In the present work, we have studied the two-photon absorption (TPA) properties of some selective molecules containing triarylborane and 1-naphthylphenylamine as the acceptor and donor moiety, respectively. The calculations are performed by using the state-of-the-art linear and quadratic response theory in the framework of the time dependent density functional theoretical method. The TPA parameters are calculated with CAMB3LYP functional and the cc-pVDZ basis set.

New design strategy for the two-photon active material based on push-pull substituted bisanthene molecule.

In the present work, we have critically examined the origin of strong two-photon transition probability of a donor-acceptor substituted bisanthene molecule that imitates a small piece of edge passivated (4, 4) graphene nanoribbon. In our calculations, we have considered -OMe, and -NH(2) as donors and -NO(2) as an acceptor. The one- and two-photon absorption parameters are evaluated using state-of-the-art linear and quadratic response theory, respectively, and all these calculations are carried out within the framework of time dependent density functional theory.