A polarizable embedding approach to second harmonic generation (SHG) of molecular systems in aqueous solutions

Giovannini, Tommaso; Ambrosetti, Matteo; Cappelli, Chiara

doi:10.1007/s00214-018-2247-7

Cited by 28 publications

(41 citation statements)

References 101 publications

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“…The model we are introducing here, ωFQ, has its fundamentals on the Fluctuating Charges (FQ) force field, which is usually adopted for describing molecular systems. [48][49][50][51][52][53] FQ places on each atom of a molecular system a charge, which is not fixed but allowed to vary as a result of differences in atomic electronegativities. Charges are regulated by atomic chemical hardness, which plays the role of an atomic capacitance.…”

Section: Theoretical Modelmentioning

confidence: 99%

A classical picture of subnanometer junctions: an atomistic Drude approach to nanoplasmonics

et al. 2019

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Section: Theoretical Modelmentioning

confidence: 99%

A classical picture of subnanometer junctions: an atomistic Drude approach to nanoplasmonics

et al. 2019

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“…In general, five models of increasing complexity will be considered: (1) Figure 2 enough to yield a converged spectrum as already pointed out by some of the present authors. [50,51,84,85] The QM/FQ convoluted and averaged spectra for molecules I-VII are reported in Figure 7. Therein the QM/PCM, QM/QM w /PCM, QM/TIP3P, QM/QM w /FQ, and experimental data are also plotted.…”

Section: Excitation Energiesmentioning

confidence: 99%

Simulating vertical excitation energies of solvated dyes: From continuum to polarizable discrete modeling

Giovannini

Macchiagodena

Ambrosetti

et al. 2018

Int J of Quantum Chemistry

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We present a computational study on the spectroscopic properties of UV-Vis absorbing dyes in water solution. We model the solvation environment by using both continuum and discrete models, with and without polarization, to establish how the physical and chemical properties of the solute-solvent interaction may affect the spectroscopic response of aqueous systems. Seven different compounds were chosen, representing different classes of organic molecules. The classical atomistic description of the solvent molecules was enriched with polarization effects treated by means of the fluctuating charges (FQ) model, propagated to the first-order response function of the quantum-mechanical (QM) solute to include its effects withing the modeling of the electronic excitations of the systems. Results obtained with the QM/FQ model were compared with those from continuum solvation models as well as nonpolarizable atomistic models, and then confronted with the experimental values to determine the accuracy that can be expected with each level of theory. Moreover, a thorough structural analysis using molecular dynamics simulations is provided for each system. K E Y W O R D S excitation energies, QM/FQ, QM/MM, QM/PCM, solvent effects, TD-DFT 1 | I N TR O DU C TI O N One-photon absorption spectroscopy within the UV-Visible range is often the most direct and inexpensive analytical tool that can be used to study the electronic properties of a system. Most commonly, such measurements are carried out on solvated samples, with water being a ubiquitous choice.With the gradual increase in the complexity of the systems under investigation, the correct interpretation of experimental data is increasingly reliant on their calculated ab initio counterparts. Many theoretical models based on quantum mechanics (QM), accompanied by their computational implementations, have been presented over the years offering different levels of compromise between the computational cost and the accuracy of the results. [1][2][3] At present, methods based on density functional theory (DFT) and its time-dependent counterpart (TD-DFT) have become the most popular choice for the simulation of absorption spectra of medium-large organic molecular systems thanks to their versatility stemming from the freedom of choice of density functional and basis set, as well as the favorable scaling with system size which allows their application to increasingly large systems. [1,[4][5][6] Many benchmarks studies have been presented elaborating on the merits and limitations of TD-DFT for the simulation of UV-Vis spectroscopy, as well as on the most appropriate choice of functional and basis set combination for different types of system. [6][7][8][9][10][11][12][13][14][15][16] And though many computational studies are carried out on isolated systems, solvent effects should not be neglected for the presence of the solvation environment can significantly alter the electronic absorption properties of a system, both qualitatively and quantitatively. [17][18][19][20][21][22][23][24][25][2...

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“…Therefore, several polarizable QM/MM approaches have been proposed, based on distributed multipoles, [35][36][37][38][39] induced dipoles, [40][41][42] Drude oscillators, 43 Fluctuating Charges (FQ) [44][45][46] and the recently developed approach based on both Fluctuating Charges and Fluctuating Dipoles (FQFµ). 47 The latter can be seen as a refinement of QM/FQ, previously developed by some of us, 46,[48][49][50][51][52][53][54] where the MM portion is described by means of electric charges, which vary as a function of differences in MM atomic electronegativities and as a response to the electric potential generated by the QM density. Therefore, in QM/FQ only monopoles, i.e.…”

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Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes

Giovannini

Riso

Ambrosetti

et al. 2019

The Journal of Chemical Physics

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Fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles, named QM/FQFµ (J. Chem. Theory Comput. 2019, 15 2233-2245), is extended to the calculation of vertical excitation energies of solvated molecular systems. Excitation energies are defined within two different solvation regimes, i.e. linear response (LR), where the response of the MM portion is adjusted to the QM transition density, and corrected-Linear Response (cLR) in which the MM response is adjusted to the relaxed QM density, thus being able to account for charge equilibration in the excited state. The model, which is specified in terms of three physical parameters (electronegativity, chemical hardness, and polarizability) is applied to vacuo-to-water 1 arXiv:1906.03852v1 [physics.chem-ph] 10 Jun 2019 solvatochromic shifts of aqueous solutions of para-nitroaniline, pyridine and pyrimidine. The results show a good agreement with their experimental counterparts, thus highlighting the potentialities of this approach. IntroductionExcited-state phenomena play a crucial role in many application fields, as for instance photocatalysis, optical information storage and solar cells. In the past decades, theoretical modeling of excited-state properties of molecules in the gas-phase has become a widespread strategy of investigation, 1 giving precious information on, for instance, the nature of the electronic excitation, 2-4 nuclei-electron coupling effects 5-7 and excited state electron dynamics. [8][9][10] However, for electronic phenomena taking place in the condensed phase, 11-19 the interplay between the molecule and its environment can substantially alter the electronic response to external electromagnetic fields. Therefore, any accurate modeling of excited states of solvated systems asks for reliable theoretical approaches to include the effects of the environment at all levels of the excitation phenomenon.Most of the currently available approaches to describe the effects of the external environment on molecular properties belong to the class of the so-called focused models; 20-25 the attention is focused on the molecule and the environment is treated a lower level of sophistication as it modifies, but not determines, the molecular response to the external radiation. In order to keep the atomistic description of the environment, thus substantially overcoming well-known and amply used continuum solvent descriptions, 23,25-29 multiscale QM/Molecular Mechanics (MM) approaches have been developed. 30,31 In such models, the molecule (solute) is treated at the QM level, whereas the environment (solvent) is modelled by means of classical MM force fields (FF). The interaction between the QM and MM portions is usually described in terms of electrostatic forces, although approaches to include non-electrostatic QM/MM interactions have been proposed recently. [32][33][34] In order to fully capure the physics of solute-

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A polarizable embedding approach to second harmonic generation (SHG) of molecular systems in aqueous solutions

Cited by 28 publications

References 101 publications

A classical picture of subnanometer junctions: an atomistic Drude approach to nanoplasmonics

A classical picture of subnanometer junctions: an atomistic Drude approach to nanoplasmonics

Simulating vertical excitation energies of solvated dyes: From continuum to polarizable discrete modeling

Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes

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