Organic molecular crystals are prevalent in pharmaceuticals and organic semiconductor materials. Physical properties such as solubility and charge carrier mobility can vary greatly with molecular arrangement within the crystal. Different crystal packing patterns of the same molecule are known as polymorphs, and accurate energy ranking of various polymorphs is often important to understanding which crystal packing motifs will occur. Finite temperature effects can reorder the relative stabilities of different polymorphs These thermal contributions can be evaluated from the lattice vibrations, or phonons, but predicting them is computationally demanding using traditional ab initio methods. Semi-empirical techniques such as density functional tight binding (DFTB) can reduce the computational cost of these calculations by up to three orders of magnitude, though the accuracy of DFTB is often lower than one what obtains from more expensive density functional theory (DFT) calculations. Here, we present a hybrid DFT/DFTB approach to phonon calculations that allows one to achieve much of the accuracy of DFT phonons at somewhat lower computational cost.

Lower-cost strategy for estimating finite-temperature effects in molecular crystals

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.