arXiv subjects

Ilana Y. Kanal

Publications and source records attributed to Ilana Y. Kanal.

3 recordsLinked to original sources

arXiv2017

A Sobering Assessment of Small-Molecule Force Field Methods for Low Energy Conformer Predictions

We have carried out a large scale computational investigation to assess the utility of common small-molecule force fields for computational screening of low energy conformers of typical organic molecules. Using statistical analyses on the energies and relative rankings of up to 250 diverse conformers of 700 different molecular structures, we find that energies from widely-used classical force fields (MMFF94, UFF, and GAFF) show unconditionally poor energy and rank correlation with semiempirical (PM7) and Kohn-Sham density functional theory (DFT) energies calculated at PM7 and DFT optimized geometries. In contrast, semiempirical PM7 calculations show significantly better correlation with DFT calculations and generally better geometries. With these results, we make recommendations to more reliably carry out conformer screening.

physics.chem-ph↗

arXiv2017

Rapid Computational Optimization of Molecular Properties using Genetic Algorithms: Searching Across Millions of Compounds for Organic Photovoltaic Materials

Conjugated organic molecules represent an important area of materials chemistry for both fundamental scientific exploration and technological applications. Using a genetic algorithm to computationally screen up to ~25-50 million molecules for organic photovoltaic properties, we find that our methods find top monomers 6,000-8,000 times faster than brute force search. By testing multiple runs and establishing convergence criteria, we show the computational scaling with search space size, common molecular motifs, and discuss the reliability to choose the same molecules independent of initial data set size. We outline remaining areas of difficulty in growing to larger search spaces, potential solutions, and filtering criteria for potential organic photovoltaic materials. Efficient genetic algorithm searches promise to address a wide range of property-driven inverse design problems in chemistry.

physics.app-ph↗

arXiv2017

Inverse Design of Conjugated Polymers from Computed Electronic Structure Properties: Model Chemistries of Polythiophenes

Using a diverse set of 100 oligothiophenes, extrapolated oligomer and polymer HOMO, LUMO and HOMO-LUMO gaps are shown to be accurately estimated from the computed values of the trimer HOMO, trimer LUMO and trimer HOMO-LUMO gaps. These simple approximations can be improved further through easy to calculate properties of monomers or small oligomers. Polymer reorganization energies, related to the hole transport, are also shown to be predicted accurately from small oligomers. Correlations between the HOMO slope with the HOMO polymer energy and HOMO-LUMO gap slope with the polymer HOMO-LUMO gap energy suggest that the degree of delocalization reflected in the slope is higher in monomers and polymers with electron-rich, less negative HOMO eigenvalues. These statistical models can serve as efficient screens for the computational prediction of polythiophene properties.

physics.app-ph↗