scholarly journals Pareto Optimization of Oligomer Polarizability and Dipole Moment using a Genetic Algorithm

2021 ◽  
Author(s):  
Danielle Hiener ◽  
Geoffrey Hutchison
Keyword(s):  
Genetic Algorithm ◽  
Dipole Moment ◽  
High Performance ◽  
Density Functional ◽  
Chemical Space ◽  
Dipole Moments ◽  
Tight Binding ◽  
Dielectric Materials ◽  
Underlying Structure ◽  
Large Set

High performance electronic components are highly sought after in order to produce increasingly smaller and cheaper electronic devices. Drawing inspiration from inorganic dielectric materials, in which both polarizability and polarization contribute, organic materials can also maximize both. For a large set of small molecules drawn from PubChem, a Pareto-like front appears between polarizability and dipole moment indicating the presence of an apparent trade-off between these two properties. We tested this balance in π-conjugated materials by searching for novel conjugated hexamers with simultaneously large polarizabilities and dipole moments with potential use for dielectric materials. Using a genetic algorithm (GA) screening technique in conjunction with an approximate density functional tight binding method (GFN2-xTB) for property calculations, we were able to efficiently search chemical space for optimal hexamers. Given the scope of chemical space, using the GA technique saves considerable time and resources by speeding up molecular searches compared to a systematic search. We also explored the underlying structure-function relationships, including sequence and monomer properties, that characterize large polarizability and dipole moment regimes.

scholarly journals Pareto Optimization of Oligomer Polarizability and Dipole Moment using a Genetic Algorithm

2021 ◽  
Author(s):  
Danielle Hiener ◽  
Geoffrey Hutchison
Keyword(s):  
Genetic Algorithm ◽  
Dipole Moment ◽  
High Performance ◽  
Density Functional ◽  
Chemical Space ◽  
Dipole Moments ◽  
Tight Binding ◽  
Dielectric Materials ◽  
Underlying Structure ◽  
Large Set

High performance electronic components are highly sought after in order to produce increasingly smaller and cheaper electronic devices. Drawing inspiration from inorganic dielectric materials, in which both polarizability and polarization contribute, organic materials can also maximize both. For a large set of small molecules drawn from PubChem, a Pareto-like front appears between polarizability and dipole moment indicating the presence of an apparent trade-off between these two properties. We tested this balance in π-conjugated materials by searching for novel conjugated hexamers with simultaneously large polarizabilities and dipole moments with potential use for dielectric materials. Using a genetic algorithm (GA) screening technique in conjunction with an approximate density functional tight binding method (GFN2-xTB) for property calculations, we were able to efficiently search chemical space for optimal hexamers. Given the scope of chemical space, using the GA technique saves considerable time and resources by speeding up molecular searches compared to a systematic search. We also explored the underlying structure-function relationships, including sequence and monomer properties, that characterize large polarizability and dipole moment regimes.

scholarly journals Dipole Moment Calculations Using Multiconfiguration Pair-Density Functional Theory and Hybrid Multiconfiguration Pair-Density Functional Theory

2021 ◽  
Author(s):  
Aleksandr Lykhin ◽  
Donald Truhlar ◽  
Laura Gagliardi
Keyword(s):  
Density Functional Theory ◽  
Dipole Moment ◽  
Density Functional ◽  
Dipole Moments ◽  
Computational Cost ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Active Space ◽  
Pair Density ◽  
Reasonable Behavior

The dipole moment is the molecular property that most directly indicates molecular polarity. The accuracy of computed dipole moments depends strongly on the quality of the calculated electron density, and the breakdown of single-reference methods for strongly correlated systems can lead to poor predictions of the dipole moments in those cases. Here, we derive the analytical expression for obtaining the electric dipole moment by multiconfiguration pair density functional theory (MC-PDFT), and we assess the accuracy of MC-PDFT for predicting dipole moments at equilibrium and nonequilibrium geometries. We show that MC-PDFT dipole moment curves have reasonable behavior even for stretched geometries, and they significantly improve upon the CASSCF results by capturing more electron correlation. The analysis of a dataset consisting of 18 first-row transition metal diatomics and 6 main-group polyatomic molecules with multireference character suggests that MC-PDFT and its hybrid extension (HMC-PDFT) perform comparably to CASPT2 and MRCISD+Q methods and have a mean unsigned deviation of 0.2–0.3 D with respect to the best available dipole moment reference values. We explored the dependence of the predicted dipole moments upon the choice of the on-top density functional and active space, and we recommend the tPBE and hybrid tPBE0 on-top choices for the functionals combined with the moderate correlated participating orbital scheme for selecting the active space. With these choices, the mean unsigned deviations (in debyes) of the calculated equilibrium dipole moments from the best estimates are 0.77 for CASSCF, 0.29 for MC-PDFT, 0.24 for HMC-PDFT, 0.28 for CASPT2, and 0.25 for MRCISD+Q. These results are encouraging because the computational cost of MC-PDFT or HMC-PDFT is largely reduced compared to the CASPT2 and MRCISD+Q methods.

scholarly journals Virtual screening of norbornadiene-based molecular solar thermal energy storage systems using a genetic algorithm

2021 ◽  
Author(s):  
Nicolai Ree ◽  
Mads Koerstz ◽  
Kurt V. Mikkelsen ◽  
Jan H. Jensen
Keyword(s):  
Genetic Algorithm ◽  
Energy Storage ◽  
Storage Systems ◽  
Chemical Space ◽  
Tight Binding ◽  
Solar Spectrum ◽  
High Energy ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Energy Storage Systems

We present a computational methodology for the screening of a chemical space of 10²⁵ substituted norbornadiene molecules for promising kinetically stable molecular solar thermal (MOST) energy storage systems with high energy densities that absorb in the visible part of the solar spectrum. We use semiempirical tight-binding methods to construct a dataset of nearly 34,000 molecules and train graph convolutional networks to predict energy densities, kinetic stability, and absorption spectra and then use the models together with a genetic algorithm to search the chemical space for promising MOST energy storage systems. We identify 15 kinetically stable molecules, five of which have energy densities greater than 0.45 MJ/kg and the main conclusion of this study is that the largest energy density that can be obtained for a single norbornadiene moiety with the substituents considered here, while maintaining a long half-life and absorption in the visible spectrum, is around 0.55 MJ/kg.

scholarly journals Substituent Effects on the Solubility and Electronic Properties of the Cyanine Dye Cy5: Density Functional and Time-Dependent Density Functional Theory Calculations

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 524
Author(s):  
Austin Biaggne ◽  
William B. Knowlton ◽  
Bernard Yurke ◽  
Jeunghoon Lee ◽  
Lan Li
Keyword(s):  
Density Functional Theory ◽  
Dipole Moment ◽  
Density Functional ◽  
Dipole Moments ◽  
Time Dependent ◽  
Cyanine Dye ◽  
Transition Dipole ◽  
Functional Theory ◽  
Solvation Energies ◽  
Transition Dipole Moments

The aggregation ability and exciton dynamics of dyes are largely affected by properties of the dye monomers. To facilitate aggregation and improve excitonic function, dyes can be engineered with substituents to exhibit optimal key properties, such as hydrophobicity, static dipole moment differences, and transition dipole moments. To determine how electron donating (D) and electron withdrawing (W) substituents impact the solvation, static dipole moments, and transition dipole moments of the pentamethine indocyanine dye Cy5, density functional theory (DFT) and time-dependent (TD-) DFT calculations were performed. The inclusion of substituents had large effects on the solvation energy of Cy5, with pairs of withdrawing substituents (W-W pairs) exhibiting the most negative solvation energies, suggesting dyes with W-W pairs are more soluble than others. With respect to pristine Cy5, the transition dipole moment was relatively unaffected upon substitution while numerous W-W pairs and pairs of donating and withdrawing substituents (D-W pairs) enhanced the static dipole difference. The increase in static dipole difference was correlated with an increase in the magnitude of the sum of the Hammett constants of the substituents on the dye. The results of this study provide insight into how specific substituents affect Cy5 monomers and which pairs can be used to engineer dyes with desired properties.

Three 1-phenylindolin-2-one derivatives displaying different molecular dipole moments and different crystallographic symmetries

2015 ◽  
Vol 71 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Lei Wang ◽  
Man Zhang ◽  
Ying-Ying Jin ◽  
Qing Lu ◽  
Qi Fang
Keyword(s):  
Density Functional Theory ◽  
Dipole Moment ◽  
Dft Calculations ◽  
Density Functional ◽  
Dipole Moments ◽  
Polar Space ◽  
Functional Theory ◽  
Polar Structure ◽  
Molecular Dipole ◽  
Space Groups

Three 1-phenylindolin-2-one derivatives, namely 1-phenylindolin-2-one, C14H11NO, (I), 5-bromo-1-phenylindolin-2-one, C14H10BrNO, (II), and 5-iodo-1-phenylindolin-2-one, C14H10INO, (III), have been synthesized and their structures determined. Compounds (I) and (II) crystallized in the centrosymmetric space groupsPbcaandP21/c, respectively, while compound (III) crystallized in the polar space groupAea2. Density functional theory (DFT) calculations show that the molecular dipole moment gradually decreases in the order (I) > (II) > (III). The relatively smaller dipole moment of (III) and the larger non-electrostatic intermolecular interactions may be the main reasons for the noncentrosymmetric and polar structure of (III).

Broadband reflectors with a disordered layered structure: statistical properties of high performing configurations selected via genetic algorithm

2022 ◽  
Author(s):  
Vincenzo Fiumara ◽  
Paolo Addesso ◽  
Francesco Chiadini ◽  
Antonio Scaglione
Keyword(s):  
Genetic Algorithm ◽  
Statistical Analysis ◽  
Layered Structure ◽  
High Performance ◽  
Dielectric Materials ◽  
High Performing ◽  
Visible Wavelength Range ◽  
Narrow Bands ◽  
Very High ◽  
Key Parameter

Abstract Disordered multilayers consisting of alternating layers of two lossless dielectric materials with random thicknesses can behave as good reflectors in wide wavelength ranges except for narrow bands where the transmittance is significative. We use a dedicated genetic algorithm to select different configurations (thickness sequences) of such structures which exhibit very low transmittance in the entire visible wavelength range, showing that broadband disordered reflectors with very high performance can be designed. A statistical analysis of the thickness sequences selected by the genetic algorithm reveals that such sequences are characterized by correlated disorder and that the degree of autocorrelation is a key parameter in determining the reflection performance.

A Selfconsistent-Charge Density-Functional Tight-Binding Scheme

1997 ◽  
Vol 491 ◽  
Author(s):  
M. Elstner ◽  
D. Porezag ◽  
G. Jungnickel ◽  
Th. Frauenheim ◽  
S. Suhai ◽  
...  
Keyword(s):  
Total Energy ◽  
Charge Density ◽  
Density Functional ◽  
Tight Binding ◽  
Density Fluctuations ◽  
Second Order ◽  
Total Charge ◽  
Charge Fluctuation ◽  
Large Set ◽  
Energy Expression

ABSTRACTWe present an extension to the tight-binding (TB) approach to improve total energies, forces and transferability in the presence of considerable long-range Coulomb interactions. We derive an approximate energy expression in terms of charge density fluctuations δn at a reference (input) density n0, which is a second order approximation to the total energy expression in density functional theory (DFT). With the choice of n0 as a superposition of densities of neutral atomic fragments, we can define a repulsive potential as in standard TB theory, which is pairwise, short ranged and transferable. The zero order terms in the total energy expression are recoverd as the standard terms of our density-functional based tight-binding (DF-TB). For the second order terms, the charge density fluctuations δn are approximated by the total charge fluctuation Δqα at atom α, which is qualitatively estimated by employing the Mullikan charge analysis. Within this approximations the total energy expression contains new parameters, which are related to ab-intio DFT calculations. Finally, by introducing localized basis functions and applying the variational principle we arrive at the Hamilton matrix elements, wich themselves depend on the charge fluctuations and, therefore, the general eigenvalue problem has to be solved self-consistently. To obtain forces for efficient geometry relaxation and molecular-dyamics, we calculated analytical derivatives of the total energy with respect to the atomic sites. In order to demonstrate the strenghts of our self-consistent-charge tight-binding (SCC-TB), we calculated reaction energies, geometries and vibrational frequencies for a large set of molecules and compare the results to semi-empirical methods, density-functional calculations and experiment.

scholarly journals Inverse Molecular Design of Alkoxides and Phenoxides for Aqueous Direct Air Capture of CO2

2021 ◽  
Author(s):  
Zisheng Zhang ◽  
Amanda L. Kummeth ◽  
Jenny Y. Yang ◽  
Anastassia N. Alexandrova
Keyword(s):  
High Performance ◽  
Density Functional ◽  
Molecular Design ◽  
Chemical Space ◽  
Binding Capacity ◽  
Poor Correlation ◽  
Co2 Absorption ◽  
Computational Screening ◽  
Direct Air Capture ◽  
Air Capture

Aqueous direct air capture (DAC) is a key technology toward a carbon negative infrastructure. Developing sorbent molecules with water- and oxygen-tolerance and high CO2 binding capacity is therefore highly desired. In this work, we analyze the CO2 absorption chemistries on amines, alkoxides, and phenoxides with density functional theory (DFT) calculations and search for the optimal sorbent using an inverse molecular design strategy. The alkoxides and phenoxides are found to be more suitable for aqueous DAC than amines thanks to their water-tolerance and capture stoichiometry of 1:1 (2:1 for amines). All three molecular systems are found to obey the same linear scaling relationship (LSR) between pK_(CO_2 ) and pK_a, since both CO2 and proton are bonded to the nucleophilic binding site through a majorly σ bonding orbital. Several high-performance alkoxides are proposed from the computational screening. In contrast, phenoxides have relatively poor correlation between pK_(CO_2 ) and pK_a, showing promise for optimization. We apply genetic algorithm (GA) to search the chemical space of substituted phenoxides for the optimal sorbent. Several promising candidates that break the LSR are discovered. The most promising off-LSR candidate phenoxides feature bulky ortho substituents forcing the CO2 adduct into a perpendicular configuration with respect to the aromatic ring. In this configuration, CO2 utilizes a different molecular orbital for binding than does the proton, and the pK_(CO_2 ) and pK_a are thus decoupled. The pK_(CO_2 )-pK_a trend and off-LSR behaviors are then confirmed by experiments, validating the inverse molecular design framework. This work not only extensively studies the chemistry of the aqueous DAC, but also presents a transferrable computational workflow for understanding and optimization of other functional molecules.

scholarly journals Accurate Receptor-Ligand Binding Free Energies from Fast QM Conformational Chemical Space Sampling

2021 ◽  
Vol 22 (6) ◽  
pp. 3078
Author(s):  
Esra Boz ◽  
Matthias Stein
Keyword(s):  
Density Functional ◽  
Chemical Space ◽  
Tight Binding ◽  
Free Ligand ◽  
Density Functional Theory Calculations ◽  
Conformational Space ◽  
Free Energies ◽  
Receptor Complexes ◽  
Experimental Values ◽  
Good Agreement

Small molecule receptor-binding is dominated by weak, non-covalent interactions such as van-der-Waals hydrogen bonding or electrostatics. Calculating these non-covalent ligand-receptor interactions is a challenge to computational means in terms of accuracy and efficacy since the ligand may bind in a number of thermally accessible conformations. The conformational rotamer ensemble sampling tool (CREST) uses an iterative scheme to efficiently sample the conformational space and calculates energies using the semi-empirical ‘Geometry, Frequency, Noncovalent, eXtended Tight Binding’ (GFN2-xTB) method. This combined approach is applied to blind predictions of the modes and free energies of binding for a set of 10 drug molecule ligands to the cucurbit[n]urils CB[8] receptor from the recent ‘Statistical Assessment of the Modeling of Proteins and Ligands’ (SAMPL) challenge including morphine, hydromorphine, cocaine, fentanyl, and ketamine. For each system, the conformational space was sufficiently sampled for the free ligand and the ligand-receptor complexes using the quantum chemical Hamiltonian. A multitude of structures makes up the final conformer-rotamer ensemble, for which then free energies of binding are calculated. For those large and complex molecules, the results are in good agreement with experimental values with a mean error of 3 kcal/mol. The GFN2-xTB energies of binding are validated by advanced density functional theory calculations and found to be in good agreement. The efficacy of the automated QM sampling workflow allows the extension towards other complex molecular interaction scenarios.

Structures and Electronic Properties of a Si55 Cluster on DFTB Calculations

2015 ◽  
Vol 815 ◽  
pp. 49-53 ◽  
Author(s):  
Li Jun Wu ◽  
Lin Zhang ◽  
Yang Qi
Keyword(s):  
Genetic Algorithms ◽  
Global Optimization ◽  
Dipole Moment ◽  
Density Functional ◽  
Tight Binding ◽  
Average Energy ◽  
Spherical Shape ◽  
Geometrical Structures ◽  
Molecular Dipole ◽  
Homo Lumo

The lowest-energy geometrical structures of a cluster containing 55 atoms were searched by using the Density Functional Tight Binding (DFTB) combined with unbiased global optimization genetic algorithms (GAs) method. Two lowest-energy structures were obtained for the Si55 cluster with the appearance of “Y shape” and “like-spherical shape” configurations. The configuration dependence average energy, highest occupied and lowest unoccupied molecular (HOMO-LUMO) gap, electron transfer and molecular dipole moment were also discussed in details for this cluster.

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