Michael Ruggiero (@mikerug.bsky.social)

🚨 New Publication in @acs.org #JCTC 🚨 We have calculated vibrational freqs and intensities for double-welled potentials in the solid state, led by Davide Mitoli from Torino, and featuring @urochester.bsky.social graduate students Maria Petrov and Will Stoll. Great work! pubs.acs.org/doi/10.1021/...

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Anharmonic Vibrational States of Double-Well Potentials in the Solid State from DFT Calculations We introduce a general approach for the simulation of quantum vibrational states of (symmetric and asymmetric) double-well potentials in molecules and materials for thermodynamic and spectroscopic applications. The method involves solving the nuclear Schrödinger equation associated with a one-mode potential of the type V(Q) = aQ2 + bQ3 + cQ4 (with a < 0 and c > 0) and thus explicitly includes nuclear quantum effects. The potential, V(Q), is obtained from density functional theory (DFT) calculations performed at displaced nuclear configurations along the selected normal mode, Q. The strategy has been implemented into the Crystal electronic structure package and allows for (i) the use of many density functional approximations, including hybrid ones, and (ii) integration with a quasi-harmonic module. The method is applied to the spectroscopic characterization of soft lattice modes in two phases of the molecular crystal of thiourea: a low-temperature ferroelectric phase and a high-temperature paraelectric phase. Signature peaks associated with structural changes between the two phases are found in the terahertz region of the electromagnetic spectrum, which exhibit strong anharmonic character in their thermal evolution, as measured by temperature-dependent terahertz time-domain spectroscopy. https://pubs.acs.org/doi/10.1021/acs.jctc.4c01394