Detecting vapour bubbles in simulations of metastable water.
The investigation of cavitation in metastable liquids with molecular simulations requires an appropriate definition of the volume of the vapour bubble forming within the metastable liquid phase. Commonly used approaches for bubble detection exhibit two significant flaws: first, when applied to water they often identify the voids within the hydrogen bond network as bubbles thus masking the signature of emerging bubbles and, second, they lack thermodynamic consistency. Here, we present two grid-based methods, the M-method and the V-method, to detect bubbles in metastable water specifically designed to address these shortcomings. The M-method incorporates information about neighbouring grid cells to distinguish between liquid- and vapour-like cells, which allows for a very sensitive detection of small bubbles and high spatial resolution of the detected bubbles. The V-method is calibrated such that its estimates for the bubble volume correspond to the average change in system volume and are thus thermodynamically consistent. Both methods are computationally inexpensive such that they can be used in molecular dynamics and Monte Carlo simulations of cavitation. We illustrate them by computing the free energy barrier and the size of the critical bubble for cavitation in water at negative pressure.
Departamento de Química Fsica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Miguel A
MA
González
Faculty of Physics and Center for Computational Materials Science, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
Georg
G
Menzl
Departamento de Química Fsica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Juan L
JL
Aragones
Faculty of Physics and Center for Computational Materials Science, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
Philipp
P
Geiger
Laboratoire de Physique de la Matiere Condensee et Nanostructures, Universite Claude Bernard, Lyon 1 et CNRS, Institut Universitaire de France, 43 boulevard du 11 novembre 1918, 69100 Villeurbanne, France.
Frederic
F
Caupin
Departamento de Química Fsica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Jose L F
JL
Abascal
Faculty of Physics and Center for Computational Materials Science, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
Christoph
C
Dellago
Departamento de Química Fsica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Chantal
C
Valeriani