Explicit Hydration of the Beryllium Trifluoride Anion with One to Three Water Molecules: BeF 3 – (H 2 O) n =1–3
Year: 2026
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide This work investigates the microhydration of the beryllium trifluoride anion (BeF 3 – ) with up to three water molecules (BeF 3 – (H 2 O) n where n = 1–3). Full geometry optimizations and harmonic vibrational frequencies were computed on various BeF 3 – (H 2 O) n stationary points using density functional theory methods (B3LYP-D3BJ, B3LYP, ωB97XD, and M06-2X) as well as the CCSD(T) and MP2 ab initio methods with a triple-ζ correlation-consistent basis set augmented with diffuse functions on all non-hydrogen atoms (haTZ). One BeF 3 – (H 2 O) 1, five BeF 3 – (H 2 O) 2 and 11 BeF 3 – (H 2 O) 3 minima were identified, most of which have not been reported in the literature to date. Two of the new BeF 3 – (H 2 O) 3 configurations have lower electronic energies than the previously reported trihydrate structure by nearly 1 kcal mol –1, but the previous structure has the lowest energy when harmonic zero-point vibrational energies are included. For the mono- and dihydrates, the water molecule(s) prefer to bind directly to the beryllium trifluoride anion via double ionic hydrogen bonds (DIHBs) to form planar structures with C 2 v symmetry. With the introduction of a third water molecule, the hydration pattern associated with the lowest-energy structure (with C 3 symmetry) changes from solely DIHBs to a hydrogen-bonded network that also includes water–water interactions. The CCSD(T)/haTZ electronic dissociation energies for the BeF 3 – (H 2 O) n global minima are 16.0, 30.1, and 43.6 kcal mol –1 for n = 1, 2, and 3, respectively, and these values decrease by about 5% when a counterpoise procedure is applied. The CCSD(T)/haTZ harmonic OH stretching frequencies of H 2 O decrease appreciably when donating hydrogen bonds to BeF 3 – and/or H 2 O molecules. The magnitude of these shifts is strongly dependent on the hydration motif. For the symmetric structures exhibiting only DIHB contacts, the largest shifts at this level of theory are −168 cm –1 for n = 1 (C 2 v ), −138 cm –1 for n = 2 (C 2 v ), and −122 cm –1 for n = 3 (D 3 h ). In contrast, the C 3 trihydrate global minimum also has hydrogen bonding between the water molecules, and the largest shift exceeds 200 cm –1 . The magnitude can even exceed 300 cm –1 in structures with an H atom that does not participate in hydrogen bonding.
Authors: Kayleigh R. Autry, Gregory S. Tschumper
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7155102542