Microscopic description of acid–base equilibrium

Acid–base reactions are ubiquitous in nature. Understanding their mechanisms is crucial in many fields, from biochemistry to industrial catalysis. Unfortunately, experiments give only limited information without much insight into the molecular behavior. Atomistic simulations could complement experim...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2019-03, Vol.116 (10), p.4054-4057
Main Authors: Grifoni, Emanuele, Piccini, GiovanniMaria, Parrinello, Michele
Format: Article
Language:English
Subjects:
Acetic acid
Acid base equilibrium
Acids
Ammonia
Aqueous solutions
Bicarbonates
Catalysis
Free energy
Molecular dynamics
Physical Sciences
Sampling
Sampling methods
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Summary:Acid–base reactions are ubiquitous in nature. Understanding their mechanisms is crucial in many fields, from biochemistry to industrial catalysis. Unfortunately, experiments give only limited information without much insight into the molecular behavior. Atomistic simulations could complement experiments and shed precious light on microscopic mechanisms. The large free-energy barriers connected to proton dissociation, however, make the use of enhanced sampling methods mandatory. Here we perform an ab initio molecular dynamics (MD) simulation and enhance sampling with the help of metadynamics. This has been made possible by the introduction of descriptors or collective variables (CVs) that are based on a conceptually different outlook on acid–base equilibria. We test successfully our approach on three different aqueous solutions of acetic acid, ammonia, and bicarbonate. These are representative of acid, basic, and amphoteric behavior.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1819771116