Computation of Solid-State Vibrational Circular Dichroism in the Periodic Gauge

Abstract

We introduce a new theoretical formalism to compute solid-state vibrational circular dichroism (VCD) spectra from molecular dynamics simulations. Having solved the origin-dependence problem of the periodic magnetic gauge, we present IR and VCD spectra of (1S,2S )-trans-1,2-cyclohexanediol obtained from first-principles molecular dynamics calculations and nuclear velocity perturbation theory, along with the experimental results. As the structure model imposes periodic boundary conditions, the common origin of the rotational strength has hitherto been ill-defined and was approximated by means of averaging multiple origins. The new formalism relies on the velocity representation of VCD and the time-correlation function, whose symmetry properties are exploited to reconnect the periodic model with the finite physical system. It restores the gauge freedom of finite models, but still allows fully accounting for non-local spatial coupling terms from the gauge transport term. We show that even for small simulation cells the rich nature of solid-state VCD spectra found in experiments can be reproduced to a very satisfactory level. While the general workflow to compute solid-state VCD spectra relies on the interplay of experimental data and theoretical simulation, expressions of VCD in liquid state and for isolated systems can be derived as simplification of the general equations.

Vibrational Circular Dichroism from DFT Molecular Dynamics: The AWV Method

“…Finally, in the case of simulations under periodic boundary conditions, the “ill definition of the common origin” problem must be addressed. One possibility is to employ a similar formalism as the one proposed by Jahnigen et al Another is to bypass the problem by averaging the predictions from multiple origins. , This latter strategy will be adopted in section via the average of the time correlation function of several independent trajectories. Because the case of disordered systems with fast enough dynamics will be discussed, this is enough to guarantee the gauge invariance of the computed spectra.…”

Photoelectron Circular Dichroism as a Signature of Subtle Conformational Changes: The Case of Ring Inversion in 1-Indanol

“…[2][3] In the IR range, its vibrational counterpart, vibrational circular dichroism (VCD), is strongly influenced by conformational isomerism and molecular interactions. [4][5][6][7][8][9][10] Despite their broad applications, these methods suffer from a lack of sensitivity and the measured effect is limited to ~10 -3 of the total absorption for ECD and even less, down to 10 -5 , for VCD. In practice the weakness of ECD makes extremely challenging its application to dilute matter in the gas phase, in particular under jet-cooled or cryogenic ion trap conditions.…”

Jet-cooled laser spectroscopy and solid-state vibrational circular dichroism of the cyclo-(Tyr-Phe) diketopiperazine dipeptide

“…IR and Vibrational circular dichroism in the solid phase: Calculation of VCD spectra in the solid state is hampered by difficulties related to the infinite nature of the crystal [39]. Although non-local effects are important for calculating VCD intensities, [40,41] approaches considering clusters of limited size can be used for obtaining reliable simulated VCD spectra [15,[42][43][44]. We use the very same approach here, starting from clusters of different sizes, whose geometry is deduced from the crystal structure with modification of the side chain arrangement, if necessary (vide infra).…”