In this work, we revisit the classic problem of homogeneous nucleation of a liquid droplet in a supersaturated vapor phase. We consider this at different extents of the driving force, or equivalently the supersaturation, and calculate a reaction coordinate (RC) for nucleation as the driving force is varied. The RC is constructed as a linear combination of three order parameters, where one accounts for the number of liquidlike atoms and the other two for local density fluctuations. The RC is calculated from biased and unbiased molecular dynamics (MD) simulations using the spectral gap optimization approach “SGOOP” [P. Tiwary and B. J. Berne, Proc. Natl. Acad. Sci. U. S. A. 113, 2839 (2016)]. Our key finding is that as the supersaturation decreases, the RC ceases to simply be the number of liquidlike atoms, and instead, it becomes important to explicitly consider local density fluctuations that correlate with shape and density variations in the nucleus. All three order parameters are found to have similar barriers in their respective potentials of mean force; however, as the supersaturation decreases, the density fluctuations decorrelate slower and thus carry longer memory. Thus, at lower supersaturations, density fluctuations are non-Markovian and cannot be simply ignored from the RC by virtue of being noise. Finally, we use this optimized RC to calculate nucleation rates in the infrequent metadynamics framework and show that it leads to a more accurate estimate of the nucleation rate with four orders of magnitude acceleration relative to unbiased MD.
Skip Nav Destination
Article navigation
21 October 2019
Research Article|
October 16 2019
Reaction coordinates and rate constants for liquid droplet nucleation: Quantifying the interplay between driving force and memory
Special Collection:
JCP Emerging Investigators Special Collection
Sun-Ting Tsai
;
Sun-Ting Tsai
1
Department of Physics and Institute for Physical Science and Technology, University of Maryland
, College Park, Maryland 20742, USA
Search for other works by this author on:
Zachary Smith
;
Zachary Smith
2
Biophysics Program and Institute for Physical Science and Technology, University of Maryland
, College Park, Maryland 20742, USA
Search for other works by this author on:
Pratyush Tiwary
Pratyush Tiwary
a)
3
Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland
, College Park, Maryland 20742, USA
Search for other works by this author on:
a)
Electronic mail: ptiwary@umd.edu
Note: This paper is part of the JCP Emerging Investigators Special Collection.
J. Chem. Phys. 151, 154106 (2019)
Article history
Received:
August 13 2019
Accepted:
September 26 2019
Citation
Sun-Ting Tsai, Zachary Smith, Pratyush Tiwary; Reaction coordinates and rate constants for liquid droplet nucleation: Quantifying the interplay between driving force and memory. J. Chem. Phys. 21 October 2019; 151 (15): 154106. https://doi.org/10.1063/1.5124385
Download citation file:
Sign in
Don't already have an account? Register
Sign In
You could not be signed in. Please check your credentials and make sure you have an active account and try again.
Sign in via your Institution
Sign in via your InstitutionPay-Per-View Access
$40.00