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

Abstract

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.

Evaluating Fast Methods for Static Polarizabilities on Extended Conjugated Oligomers

“…For example, because of its vast speed-up compared to ab initio methods, we previously used GFN2/D4 to calculate the polarizabilities of novel hexamer structures generated by a genetic algorithm (GA)-driven search for high-dielectric organic conjugated oligomers. 8 For that work, we chose to use GFN2/D4 despite suspecting a degree of inaccuracy at high polarizabilities. The speed-up GFN2/D4 provides over DFT methods was necessary to complete the thousands of hexamer polarizability calculations in a reasonable amount of computation time.…”

“…As shown in our previous work using a genetic algorithm (GA) to search for high dielectric oligomers, there is a need for a polarizability method capable of calculating large polarizabilities (on the scale of 10 2 Å3 ) while making e cient use of time and computational resources. 8 As a point of reference, all of the molecular species examined by the previously mentioned studies possess isotropic polarizabilities less than 40 Å3 .…”

“…5 Computationally-derived Raman spectra also rely on the calculation of polarizability tensors. 6 Polarizability values are also necessary to calculate the values of more complex material properties such as refractive index 7 and dielectric constant, 8 often in the context of molecular screening.…”

Inverse Design of Tetracene Polymorphs with Enhanced Singlet Fission Performance by Property-Based Genetic Algorithm Optimization

“…An advantage of a GA over other methods is that the fitness function can be formulated to optimize any property of interest. GAs with tailor-made fitness functions have been used, for example, to optimize the electronic, 85 optical, 86 and excitonic 87 properties of materials, as well as transport properties of organic semiconductor molecules. 88 Unlike the global minimum search of traditional CSP, a property-based GA does not necessarily yield one optimum but a set of solutions with the target property and stability within an acceptable range.…”