Showing papers on "Polarizable continuum model published in 2016"
TL;DR: This study shows that the ωB97XD functional with the 6-31+G(d,p) and 6-311++G( d, p) basis sets, and the SMD solvation model with three explicit water molecules hydrogen bonded to the sulfur produces the best result for the test set.
Abstract: The pKa’s of substituted thiols are important for understanding their properties and reactivities in applications in chemistry, biochemistry, and material chemistry. For a collection of 175 different density functionals and the SMD implicit solvation model, the average errors in the calculated pKa’s of methanethiol and ethanethiol are almost 10 pKa units higher than for imidazole. A test set of 45 substituted thiols with pKa’s ranging from 4 to 12 has been used to assess the performance of 8 functionals with 3 different basis sets. As expected, the basis set needs to include polarization functions on the hydrogens and diffuse functions on the heavy atoms. Solvent cavity scaling was ineffective in correcting the errors in the calculated pKa’s. Inclusion of an explicit water molecule that is hydrogen bonded with the H of the thiol group (in neutral) or S– (in thiolates) lowers error by an average of 3.5 pKa units. With one explicit water and the SMD solvation model, pKa’s calculated with the M06-2X, PBEPBE,...
131 citations
TL;DR: This approach represents an easily applicable and computationally efficient tool to estimate the gas-to-crystal phase shifts of the frontier-orbital quasiparticle energies in organic electronic materials.
Abstract: We propose a new methodology for the first-principles description of the electronic properties relevant for charge transport in organic molecular crystals. This methodology, which is based on the combination of a nonempirical, optimally tuned range-separated hybrid functional with the polarizable continuum model, is applied to a series of eight representative molecular semiconductor crystals. We show that it provides ionization energies, electron affinities, and transport gaps in very good agreement with experimental values, as well as with the results of many-body perturbation theory within the GW approximation at a fraction of the computational costs. Hence, this approach represents an easily applicable and computationally efficient tool to estimate the gas-to-crystal phase shifts of the frontier-orbital quasiparticle energies in organic electronic materials.
112 citations
SIDI1
TL;DR: The study of structural, electronics and optical properties for these compounds could help to design more efficient functional photovoltaic organic materials.
Abstract: Novel six organic donor-π-acceptor molecules (D-π-A) used for Bulk Heterojunction organic solar cells (BHJ), based on thienopyrazine were studied by density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches, to shed light on how the π-conjugation order influence the performance of the solar cells The electron acceptor group was 2-cyanoacrylic for all compounds, whereas the electron donor unit was varied and the influence was investigated The TD-DFT method, combined with a hybrid exchange-correlation functional using the Coulomb-attenuating method (CAM-B3LYP) in conjunction with a polarizable continuum model of salvation (PCM) together with a 6-31G(d,p) basis set, was used to predict the excitation energies, the absorption and the emission spectra of all molecules The trend of the calculated HOMO–LUMO gaps nicely compares with the spectral data In addition, the estimated values of the open-circuit photovoltage (Voc) for these compounds were presented in two cases/PC60BM and/PC71BM The study of structural, electronics and optical properties for these compounds could help to design more efficient functional photovoltaic organic materials
80 citations
TL;DR: In this paper, a recently developed integrated Quantum-Mechanical/Polarizable molecular mechanics (MM)/polarizable continuum model (PCM) method is discussed, which combines a fluctuating charge approach to the MM polarization with the PCM.
Abstract: Solvent effects on chiroptical properties and spectroscopies can be huge, and affect not only the absolute value but the sign of molecular chiroptical responses. Therefore, the definition of reliable theoretical models and computational protocols to calculate chiroptical responses and assist the assignment of the chiral absolute configuration cannot overlook the effects of the surrounding environment. Continuum solvation methodologies are successful in case of weakly interacting solute–solvent couples, whereas in case of strongly interacting systems, such as those dominated by explicit hydrogen bonding interaction, a change of strategy is required to gain a reliable modeling. In this review, a recently developed integrated Quantum-Mechanical/Polarizable molecular mechanics (MM)/polarizable continuum model (PCM) method is discussed, which combines a fluctuating charge approach to the MM polarization with the PCM. Its theoretical fundamentals, and issues related to the calculation of chiroptical responses are summarized, and the application to few representative test cases in aqueous solution is discussed.
76 citations
TL;DR: The ability of long-range corrected (LCR) hybrid functionals in combination with the polarizable continuum model (PCM) to determine the impact of the solid-state environment on the CT states is discussed.
Abstract: Density functional theory (DFT) approaches based on range-separated hybrid functionals are currently methods of choice for the description of the charge-transfer (CT) states in organic donor/acceptor solar cells. However, these calculations are usually performed on small-size donor/acceptor complexes and as result do not account for electronic polarization effects. Here, using a pentacene/C60 complex as a model system, we discuss the ability of long-range corrected (LCR) hybrid functionals in combination with the polarizable continuum model (PCM) to determine the impact of the solid-state environment on the CT states. The CT energies are found to be insensitive to the interactions with the dielectric medium when a conventional time-dependent DFT/PCM (TDDFT/PCM) approach is used. However, a decrease in the energy of the CT state in the framework of LRC functionals can be obtained by using a smaller range-separated parameter when going from an isolated donor/acceptor complex to the solid-state case.
66 citations
TL;DR: The energy and its analytic gradient are formulated for the fragment molecular orbital (FMO) method combined with density-functional tight-binding (DFTB) and the polarizable continuum model (PCM), and the accuracy is demonstrated in comparison with unfragmented calculations and numerical gradients.
Abstract: The energy and its analytic gradient are formulated for the fragment molecular orbital (FMO) method combined with density-functional tight-binding (DFTB) and the polarizable continuum model (PCM). The accuracy is demonstrated in comparison with unfragmented calculations and numerical gradients. The instability in the description of proteins using density functional theory (DFT) and DFTB is analyzed for both unfragmented and FMO methods. The cause of the instability is shown to be charged residues, and the problem is particularly severe in the gas phase when long-range functionals are not used. Adding solvent effects considerably increases the gap between occupied and virtual orbitals and stabilizes convergence. The pair interaction energies calculated using FMO-DFT and FMO-DFTB in solution are shown to correlate, whereas the latter method is 4840 times faster than the former for a protein consisting of 1961 atoms. The structures of five proteins (containing up to 3578 atoms) optimized using FMO-DFTB/PCM agree reasonably well with experiment.
56 citations
TL;DR: The application of this methodology to calculate Vibrational Circular Dichroism spectra of chiral systems in aqueous solution gives calculated spectra in remarkable agreement with their experimental counterparts and a substantial improvement with respect to the same spectra calculated with the PCM.
Abstract: We propose a methodology, based on the combination of classical Molecular Dynamics (MD) simulations with a fully polarizable Quantum Mechanical (QM)/Molecular Mechanics (MM)/Polarizable Continuum Model (PCM) Hamiltonian, to calculate Vibrational Circular Dichroism (VCD) spectra of chiral systems in aqueous solution. Polarization effects are included in the MM force field by exploiting an approach based on Fluctuating Charges (FQ). By performing the MD, the description of the solvating environment is enriched by taking into account the dynamical aspects of the solute–solvent interactions. On the other hand, the QM/FQ/PCM calculation of the VCD spectrum ensures an accurate description of the electronic density of the solute and a proper account for the specific interactions in solution. The application of our approach to (R)-methyloxirane and (l)-alanine in aqueous solution gives calculated spectra in remarkable agreement with their experimental counterparts and a substantial improvement with respect to the...
54 citations
TL;DR: In this paper, a non-empirical, optimally tuned range-separated (RS) functional combining with the polarizable continuum model (PCM) was used to predict ionization energies, electron affinities, transport gaps, optical gaps, and exciton binding energies of six polythiophene-derived polymers.
Abstract: Exciton binding energies of six polythiophene-derived polymers were studied through using a nonempirical, optimally tuned range-separated (RS) functional combining with the polarizable continuum model (PCM). We demonstrate that this approach predicts ionization energies (IE), electron affinities (EA), transport gaps, optical gaps, and exciton binding energies of six different polymer chains in both vacuum and solid (dielectric medium) with accuracy comparable to many-body perturbation theory within the GW approximation and Bethe–Salpeter equation (BSE). Furthermore, the behavior of exciton binding energy versus dielectric constant was also reasonably described by the PCM-tuned RS functional, whereas the conventional functionals such as PBE, B3LYP, M062X, and nontuned LC-ωPBE completely fail. We believe our method provides for a reliable and computationally efficient tool for future investigation of efficiency-enhancing mechanism and molecular design in organic solar cells.
52 citations
TL;DR: In this paper, the self-consistent reaction field theory was used to investigate the solvent effects on the structure and electronic properties of the hybride of Pd doped single-walled carbon nanotube (Pd/SWCNT) and histidine amino acid as a new generation of nanobiosensors.
50 citations
TL;DR: The polarizable continuum model within the framework of the many-body Green's function GW formalism for the calculation of electron addition and removal energies in solution opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology.
Abstract: We have implemented the polarizable continuum model within the framework of the many-body Green’s function GW formalism for the calculation of electron addition and removal energies in solution. The present formalism includes both ground-state and non-equilibrium polarization effects. In addition, the polarization energies are state-specific, allowing to obtain the bath-induced renormalisation energy of all occupied and virtual energy levels. Our implementation is validated by comparisons with ΔSCF calculations performed at both the density functional theory and coupled-cluster single and double levels for solvated nucleobases. The present study opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology.
50 citations
TL;DR: The solvated electron (e(aq)⁻) is a primary intermediate after an ionization event that produces reductive DNA damage and reacts with guanine only when a water molecule forms a hydrogen bond to O6 of guanines which stabilizes the anion radical.
Abstract: The solvated electron (eaq–) is a primary intermediate after an ionization event that produces reductive DNA damage. Accurate standard redox potentials (Eo) of nucleobases and of eaq– determine the extent of reaction of eaq– with nucleobases. In this work, Eo values of eaq– and of nucleobases have been calculated employing the accurate ab initio Gaussian 4 theory including the polarizable continuum model (PCM). The Gaussian 4-calculated Eo of eaq– (−2.86 V) is in excellent agreement with the experimental one (−2.87 V). The Gaussian 4-calculated Eo of nucleobases in dimethylformamide (DMF) lie in the range (−2.36 V to −2.86 V); they are in reasonable agreement with the experimental Eo in DMF and have a mean unsigned error (MUE) = 0.22 V. However, inclusion of specific water molecules reduces this error significantly (MUE = 0.07). With the use of a model of eaq–-nucleobase complex with six water molecules, the reaction of eaq– with the adjacent nucleobase is investigated using approximate ab initio molecula...
TL;DR: In this article, the authors investigated six anion-molecule nucleophilic substitution reactions in methanol and dipolar aprotic solvents, and showed that the SMD model is not adequate for dipolar anion to dipolar acid solvent rate acceleration effect.
Abstract: In the past seven years, the SMD (Solvent Model Density) method has been widely used by computational chemists. Thus, assessment on the reliability of this model for modeling chemical process in solution is worthwhile. In this report, it was investigated six anion-molecule nucleophilic substitution reactions in methanol and dipolar aprotic solvents. Geometry optimizations have been done at SMD/X3LYP level and single point energy calculations at CCSD(T)/TZVPP + diff level. Our results have indicated that the SMD model is not adequate for dipolar aprotic solvents, with a root of mean squared (RMS) error of 5.6 kcal mol-1, while the Polarizable Continuum Model (PCM) method with the Pliego and Riveros atomic cavities has led to RMS error of only 3.2 kcal mol-1. For methanol solvent, the SMD method has a RMS error of 3.0 kcal mol-1. The classical protic to dipolar aprotic solvent rate acceleration effect was not predicted by the SMD model for the tested systems.
TL;DR: This work compares molecular mechanical fixed point charges to a polarizable continuum model (PCM) for computing electronic excitations in solution and computed the excitation energy of three pairs of neutral/anionic molecules in aqueous solvent, including up to 250 water molecules in the QM region.
Abstract: Mixed quantum mechanical (QM)/classical methods provide a computationally efficient approach to modeling both ground and excited states in the condensed phase To accurately model short-range interactions, some amount of the environment can be included in the QM region, whereas a classical model can treat long-range interactions to maintain computational affordability The best computational protocol for these mixed QM/classical methods can be determined by examining convergence of molecular properties Here, we compare molecular mechanical (MM) fixed point charges to a polarizable continuum model (PCM) for computing electronic excitations in solution We computed the excitation energy of three pairs of neutral/anionic molecules in aqueous solvent, including up to 250 water molecules in the QM region Interestingly, the convergence is similar for MM point charges and a PCM, with convergence achieved when at least one full solvation shell is treated with QM Although the van der Waals (VDW) definition of t
TL;DR: In this article, a molecular modeling analysis via density functional theory has been performed on all possible conformers of acetaminophen and the optimized structures, total energies, energy gap, chemical potential, global hardness, softness, global electrophilicity and dipole moments were calculated.
TL;DR: The results show that both solvent polarity and relative strength of the donor groups have significant impact on the electric properties, but more strikingly on the first hyperpolarizability β.
Abstract: We calculated the nonlinear optical properties of 24 azo-enaminone derivatives, incorporating solvent effects on their geometric and electronic structure, to assess the impact of the environment on these properties. Namely, we incorporated chloroform, tetrahydrofuran, acetone, ethanol, methanol, and dimethyl sulfoxide in our calculations and compared our results incorporating solvent effects with our gas-phase calculations. To account for the electron correlation effects on NLO properties, we performed the calculations at MP2/6-31G(p)//MP2/6-31G(d) level set. The polarizable continuum model was used to simulate the presence of the solvent. The exponents of p extra functions added to heavy atoms were obtained, imposing the maximization of the first hyperpolarizability. Two structural configurations (Z and E) of azo-enaminones were investigated to assess the isomeric effects of the electric properties. Our results show that both solvent polarity and relative strength of the donor groups have a significant i...
TL;DR: In this article, the most stable geometrical parameters of structures in this study were optimized at the B3LYP/6-311++G(d,p) level by employing the Gaussian09 program.
Abstract: Carbon dioxide capture by amine-functionalized ionic liquids (IL), 1,2-dimethyl-(3-aminoethyl)imidazolium fluoride ([aEMMIM][F]), [aEMMIM][Cl], [aEMMIM][Br], and [aEMMIM][I] were synthesized and characterized by both DFT simulation and experimental methods. The most stable geometrical parameters of structures in this study were optimized at the B3LYP/6-311++G(d,p) level by employing the Gaussian09 program. The results showed that CO2 can be chemically captured in ILs by forming carbamic acid with a 1 : 1 molar ratio stoichiometry. DFT simulations were performed to investigate the configuration variations of the reactants, intermediates, transition states and products, as well as energy barriers and vibration frequency changes in the gas phase using the conductor-like polarizable continuum model (CPCM) in an aqueous solution. The vibration frequency obtained in DFT simulation was consistent with the experimental result by employing a scaling factor. AIM and NBO analysis were also carried out to investigate the nature and features of the studied structures at the molecular level.
TL;DR: In this paper, the title compound, 2-Ethyl-N-[(5-nitrothiophene-2-yl)methylidene]aniline, C13H12N2O2S, has been synthesized and characterized by FT-IR and UV-Vis spectrum.
TL;DR: The mechanism of acetonitrile and methyl benzoate catalytic hydrogenation using pincer catalysts has been computed at various levels of density functional theory and the computed equilibrium between 1Fe and 2Fe agrees perfectly with the experimental observations.
Abstract: The mechanism of acetonitrile and methyl benzoate catalytic hydrogenation using pincer catalysts M(H)2(CO)[NH(C2H4PiPr2)2] (1M) and M(H)(CO)[N(C2H4PiPr2)2] (2M) (M = Fe, Ru, Os) has been computed at various levels of density functional theory. The computed equilibrium between 1Fe and 2Fe agrees perfectly with the experimental observations. On the basis of the activation barriers and reaction energies, the best catalysts for acetonitrile hydrogenation are 1Fe/2Fe and 1Ru/2Ru, and the best catalysts for methyl benzoate hydrogenation are 1Ru/2Ru. The best catalysts for the dehydrogenation of benzyl alcohol are 1Ru/2Ru. It is to note that the current polarizable continuum model is not sufficient in modeling the solvation effect in the energetic properties of these catalysts as well as their catalytic properties in hydrogenation reaction, as no equilibrium could be established between 1Fe and 2Fe. Comparison with other methods and procedures has been made. © 2015 Wiley Periodicals, Inc.
TL;DR: This work presents an extension of one such multiscale model, originally inspired by the polarizable continuum model, to a real-time description of the electronic dynamics of the molecule and of the NP, and adopts a time-dependent configuration interaction approach for the molecule.
Abstract: The optical properties of molecules close to plasmonic nanostructures greatly differ from their isolated molecule counterparts. To theoretically investigate such systems from a quantum-chemistry perspective, one has to take into account that the plasmonic nanostructure (e.g., a metal nanoparticle–NP) is often too large to be treated atomistically. Therefore, a multiscale description, where the molecule is treated by an ab initio approach and the metal NP by a lower level description, is needed. Here we present an extension of one such multiscale model [Corni, S.; Tomasi, J. J. Chem. Phys. 2001, 114, 3739], originally inspired by the polarizable continuum model, to a real-time description of the electronic dynamics of the molecule and of the NP. In particular, we adopt a time-dependent configuration interaction (TD CI) approach for the molecule, the metal NP is described as a continuous dielectric of complex shape characterized by a Drude–Lorentz dielectric function, and the molecule–NP electromagnetic cou...
TL;DR: In this paper, the optoelectronic properties of five types triphenylamine (TPA)-based dyes, namely, C206, TPA, N(CH3)2 and TPA-SCH3, have been investigated by Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT).
Abstract: Designed metal-free dyes have been investigated by Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) to evaluate the ground state and excited state geometries of triphenylamine-based organic sensitizers. The optoelectronic properties of five types triphenylamine (TPA)-based dyes, namely, C206, TPA, TPA-N(CH3)2, TPA-SCH3, and TPA-OC2H5, were studied. Energy band modulation has been performed for these dyes with different electron donating groups and the same electron withdrawing group. The performance of the hybrid functionals B3LYP and wB97XD using a standard basis set, 6-311++G(d,p), has been analyzed. Solvent effects have been examined by Conductor-like Polarizable Continuum Model (C-PCM) formalisms. The C-PCM/TD-DFT results show that accurate absorption energies are obtained only when the solvent effect is included in the excited state geometries. Theoretical examination of the non-linear optical (NLO) properties was performed on the key parameters of static polarizability and first order and second order hyperpolarizability. Good photovoltaic performance based on the optimized geometry, the relative position of the frontier molecular orbital energy levels and the absorption maxima of the dye are expected for offering a remarkable response. The results provide a direction for optimizing dyes as efficient sensitizers in dye-sensitized solar cells (DSSCs) and NLO applications.
TL;DR: In this article, specific chemical interactions affecting the prediction of one-electron and twoelectron reduction potentials for anthraquinone derivatives are investigated and the best theoretical estimations result in a good correlation with experiments, V(Theory) = 0.903V(Expt) + 0.007 with an R2 value of 0.835.
Abstract: In this combined computational and experimental study, specific chemical interactions affecting the prediction of one-electron and two-electron reduction potentials for anthraquinone derivatives are investigated. For 19 redox reactions in acidic aqueous solution, where AQ is reduced to hydroanthraquinone, density functional theory (DFT) with the polarizable continuum model (PCM) gives a mean absolute deviation (MAD) of 0.037 V for 16 species. DFT(PCM), however, highly overestimates three redox couples with a MAD of 0.194 V, which is almost 5 times that of the remaining 16. These three molecules have ether groups positioned for intramolecular hydrogen bonding that are not balanced with the intermolecular H-bonding of the solvent. This imbalanced description is corrected by quantum mechanics/molecular mechanics (QM/MM) simulations, which include explicit water molecules. The best theoretical estimations result in a good correlation with experiments, V(Theory) = 0.903V(Expt) + 0.007 with an R2 value of 0.835...
TL;DR: It is shown that it is possible to build accurate force fields for small organic molecules allowing the reliable reproduction of a large panel of bulk properties, which are seldom addressed in the same context as hydrogen bond patterns and reorientational lifetimes.
Abstract: In this contribution we show that it is possible to build accurate force fields for small organic molecules allowing the reliable reproduction of a large panel of bulk properties, which are seldom addressed in the same context. Starting from the results obtained in recent studies, we developed a protocol for charge estimation and virtual site generation for the amide class of molecules. The parametrization of electrostatic properties is based on population analysis and orbital localization of quantum mechanical computations rooted in density functional theory and the polarizable continuum model, without any additional external information. The new protocol, coupled to other recent studies in our group targeted at an accurate fitting of internal degrees of freedom, makes available a method for building force fields from scratch (excluding for the moment intermolecular van der Waals interactions) with focus on reproducing the structure and dynamics of hydrogen bonded liquids, yielding results that are in line or better than those delivered by current general force fields. The approach is tested on the demanding series formed by formamide and its two N-methyl derivatives, N-methylformamide and N,N-dimethylformamide. We show that the atomistic structure of the liquids arising from classical molecular dynamics (MD) simulations employing the new force field is in full agreement with X-ray and neutron diffraction experiments and the corresponding spatial distribution functions are in remarkable agreement with the results of ab initio MD simulations. It is noteworthy that the latter result has never been obtained before without using ad hoc (and system dependent) scale factors and that, in addition, our parameter-free procedure is able to reproduce static dielectric constants over a wide range of values without sacrificing the force field accuracy with respect to other observables. Finally, we are able to explain the trend of static dielectric constants followed by the three amides in terms of properties obtained from the simulations, namely hydrogen bond patterns and reorientational lifetimes.
TL;DR: In this paper, the first shell around the lithium ion is fully occupied with four ethylene carbonate (EC) molecules in both gas phase and solvent, and the contribution of vibration entropy to free energy of isomers of [Li(EC)n]+ reveals that the best candidates at zero-temperature cannot be maintained at finite temperatures due to the effects of their vibration entropy.
Abstract: The coordination and energetics of low-lying structures of [Li(EC)n]+ have been analyzed by density functional theory (DFT) and polarizable continuum model (PCM) at the B3LYP/6-311+G (d, p) level. The results show that the first shell around the lithium ion is fully occupied with four ethylene carbonate (EC) molecules in both gas phase and solvent. The examination on the contribution of vibration entropy to free energy of isomers of [Li(EC)n]+ reveals that the stability of the best candidates at zero-temperature cannot be maintained at finite temperatures due to the effects of their vibration entropy. In addition, structural transitions between the most stable four-coordinated and the metastable three-coordinated structure demand a very low energy barrier, suggesting that at a finite temperature the four-coordinated and three-coordinated isomers of [Li(EC)n]+ can coexist in the EC organic solvent lithium salt electrolyte. © 2015 Wiley Periodicals, Inc.
TL;DR: This approach incorporates an accurate electronic charge distribution of the solute within a molecular-shaped cavity in conjunction with a dielectric continuum treatment of the solvent, ions, and electrode using the integral equations formalism polarizable continuum model.
Abstract: Electron transfer and proton coupled electron transfer (PCET) reactions at electrochemical interfaces play an essential role in a broad range of energy conversion processes. The reorganization energy, which is a measure of the free-energy change associated with solute and solvent rearrangements, is a key quantity for calculating rate constants for these reactions. We present a computational method for including the effects of the double layer and ionic environment of the diffuse layer in calculations of electrochemical solvent reorganization energies. This approach incorporates an accurate electronic charge distribution of the solute within a molecular-shaped cavity in conjunction with a dielectric continuum treatment of the solvent, ions, and electrode using the integral equations formalism polarizable continuum model. The molecule-solvent boundary is treated explicitly, but the effects of the electrode-double layer and double layer-diffuse layer boundaries, as well as the effects of the ionic strength o...
TL;DR: In this article, the organic crystal 4-aminopyridinium 4-hydroxy benzoate hydrate was grown using slow evaporation method and various characterization techniques were employed to assay the structure and properties of the grown crystal.
TL;DR: In this paper, the photophysical properties of dicyanovinyl-thienylpyrroles 1-6 compounds were investigated by the determining of the first-order molecular static hyperpolarizability (β) and the second-order MSSI (γ) in the ground state by using the HSEh1PBE/6-311G(d,p) level of density functional theory.
TL;DR: A new algorithm to solve the polarizable continuum model equation in a framework compatible with the strategy previously developed by us for the conductor-like screening model based on Schwarz's domain decomposition method (ddCOSMO).
Abstract: We present a new algorithm to solve the polarizable continuum model equation in a framework compatible with the strategy previously developed by us for the conductor-like screening model based on Schwarz's domain decomposition method (ddCOSMO). The new discretization is systematically improvable and is fully consistent with ddCOSMO so that it reproduces ddCOSMO results for large dielectric constants.
TL;DR: A systematic computational study of the vibrationally resolved one- and two-photon absorption spectra in vacuum and in solution of bis(BF2) core complexes finds that the polarizable embedding CC2 and the state-specific PCM are the most successful approaches for description of environmental broadening.
Abstract: Motivated by the outstanding properties of bis(BF2) core complexes as fluorophore probes, we present a systematic computational study of their vibrationally resolved one- and two-photon absorption spectra in vacuum and in solution. Electronic and vibrational structure calculations were performed using the coupled cluster CC2 method and the Kohn-Sham formulation of density functional theory (DFT). A nonempirical estimation of the inhomogeneous broadening, accomplished using the polarizable embedding (PE) approaches combined with time-dependent DFT and CC2 methods, is used as a key ingredient of the computational protocol employed for simulations of the spectral features in solution. The inhomogeneous broadening is also determined based on the Marcus theory employing linear response and state-specific polarizable continuum model (PCM) methods. It is found that the polarizable embedding CC2 and the state-specific PCM are the most successful approaches for description of environmental broadening. For the 1(1)A(g) → 1(1)B(u) transition, the non-Condon effects can be safely neglected and a fair agreement between the simulated and experimental band shapes is found. In contrast, the shape of the vibrationally resolved band corresponding to the two-photon allowed 1(1)A(g) → 2(1)A(g) transition is largely dominated by non-Condon effects. A generalized few-level model was also employed to analyze the mechanism of the electronic two-photon 1(1)A(g) → 2(1)A(g) excitation. It was found that the most important optical channel involves the 1(1)B(u) excited state. Ramifications of the findings for general band shape modeling are briefly discussed.
TL;DR: In this article, the ground-state geometries of selected anthoxanthins belonging to the Flavone and Flavonol families were optimized by Density-Functional Theory (DFT).
Abstract: Systematic theoretical investigations of selected anthoxanthins belonging to the Flavone and Flavonol families are carried out with the aim of identifying the dye with the optimum properties for use as sensitizers in dye sensitized solar cells (DSSCs). The ground-state geometries of these dyes in the gas phase are fully optimized by Density-Functional Theory (DFT). Time-Dependent Density Functional Theory (TDDFT) with Polarizable Continuum Model (PCM) for solvent effects is invoked to predict the vertical electron excitation energy, maximal absorption wavelength, oscillator strengths, light harvesting efficiency (LHE), free energy change of electron injection $$\left( {\Delta } G^{inject}\right) $$ΔGinject and dye regeneration $$\left( {\Delta } G_{dye}^{regen}\right) $$ΔGdyeregen. The charge transfer from the excited state and charge regeneration in the ground state of the dyes is also identified. All these calculations were performed in the gas phase and with dimethyl sulfoxide (DMSO) as solvent. Finally, the electron transfer characteristics between the dye's lowest unoccupied molecular orbital (LUMO) and the conduction band of $$\hbox {TiO}_{2}$$TiO2 are investigated. The study reveals that the electron transfer character of these dyes can be made suitable for applications in DSSCs with structural modifications.
TL;DR: In this paper, the absorption and emission spectra of the fluorescent dyes Nile blue (NB) and Nile red (NR) were simulated with different methods, considering the effect of water as solvent.
Abstract: The absorption and emission spectra of the fluorescent dyes Nile blue (NB) and Nile red (NR), widely used in biology and histology, were simulated with different methods, considering the effect of water as solvent. The aforementioned dyes are extremely significant because they also act as DNA sensitizers and hence can be used in photodynamic therapy. Especially, time dependent-density functional theory (TD-DFT) including different functionals, and ab initio single-state- and multi-state-complete active space perturbation theory (SS- and MS-CASPT2) including the effect of the basis set, were considered. The solvent environment was taken into account statically and dynamically: static optical properties were calculated with the polarizable continuum model as vertical transitions from the ground state equilibrium geometry, while dynamic properties were obtained by performing ground state molecular dynamics of NB and NR in explicit water, followed by hybrid quantum mechanics/molecular mechanics calculations of a statistical number of geometries along the trajectory. The results show that a dynamic treatment is required in order to reproduce the experimental absorption spectra, since the static approach gives rise to a hypsochromic shift of ca. 0.3 eV for NB and 0.2 eV for NR, at the TD-DFT and CASPT2 level of theory. This can be explained in terms of out-of-plane vibrational normal modes, which are properly taken into account only in the dynamic approach. Moreover, an exhaustive description of the charge transfer character in the excited state is given, at both TD-DFT and CASPT2 levels of theory.