# The Hydration of Trifluoroacetic Acid from 0 to 298 K

## TL;DR

This study investigates how trifluoroacetic acid interacts with water molecules at different temperatures, finding it unlikely to contribute to cloud formation.

## Contribution

The paper provides new insights into TFA hydration structures and their atmospheric relevance using high-level quantum calculations.

## Key findings

- Low-energy TFA-water cluster structures were identified at 0 to 298 K.
- TFA clusters n = 1–2 are predicted to be abundant near Earth's surface.
- Larger TFA-water clusters are absent, suggesting minimal role in new particle formation.

## Abstract

Trifluoroacetic acid
(TFA), the most atmospherically
abundant perfluorocarbocylic
acid, is a molecule of increasing environmental and biological significance.
In this paper, we examine TFA’s role in new particle formation
(NPF), a critical yet lesser-understood step in cloud formation in
which aerosols that act as cloud condensation nuclei are formed. We
used conformational sampling to find low-energy structures for TFA-nH2O (n = 1–8) clusters
and determined accurate DLPNO–CCSD­(T)/haug-cc-pV5Z//ωB97X-D/6–31++G**
enthalpies at 0 K and Gibbs free energies at 216.65, 273.15, and 298.15
K. Then, atmospheric concentrations were determined at relevant atmospheric
temperatures. Rotational constants for the lowest energy n = 1–3 structures corroborate existing microwave spectroscopic
data, validating our methodology. Additionally, spectroscopic properties
for n = 4–8 structures were identified for
comparison with future experimental findings. All lowest energy structures
were found to have neutral, rather than ion-pair monomers. Near Earth's
surface, we predict significant concentrations of n = 1–2 clusters (2.06 × 105 molecules cm–3 and 1.13 × 104, respectively); however,
the absence of larger clusters indicates that TFA likely serves a
negligible role in NPF.