Surface of annealed silica. Undercoordinated silicon atoms are bound to only three oxygen atoms. Undercoordinated oxygen atoms are bound to only one silicon atom. [Image generated with QUTEMOL (Ref. 29).]
System snapshot: z-axis shown as horizontal. Oxygen (red), hydrogen (white), and silicon (yellow) atoms shown. [Image generated with QUTEMOL (Ref. 29).]
Reax force field validation.
Water charge distribution. Water molecule charge is distributed about neutral, with oxygen and hydrogen charges distributed about and , respectively.
Water RDF: RDF between oxygen-oxygen (O–O), hydrogen-hydrogen (H–H), and oxygen-hydrogen (O–H) shown for bulk water.
Water MSD: mean squared displacement shown for oxygen and hydrogen atoms within a pure water system.
Silica RDF: RDFs in pure silica shown for oxygen-oxygen (O–O), silicon-silicon (Si–Si), and silicon-oxygen (Si–O).
Mass densities: Mass densities for the interfacial system, illustrating the locations of the Gibbs dividers (dashed). Included is density of oxygen (red), hydrogen (teal), silicon (blue), and the total (green).
Silica-water interfacial area. [Image generated with QUTEMOL (Ref. 29).]
Species quantities: the number of water molecules (c), silanol molecules (d), NBO atoms (b), and undercoordinated silicon atoms (a).
Water dipole moment: orientation of water molecules given as cosine of the angle between dipole moment and surface normal (z-axis). Error bars are given as inverse square-root of number of water molecules. Gibbs dividers (dashed line) shown for reference.
Electric potential: averaged over both halves of the interface. Distance (z) shown is distance from the center of the silica slab.
Water data. Reax results compared with ab initio, SPC/E, and experimental. Water bond length is given as . RDF minimum and maximum values are local min and max. Diffusion is atomic self-diffusion.
Silica data. Pure silica in Reax computed with MD and experiment. Silicon oxygen bond is given as . Max and min RDF values are local min and max values. Coordination is calculated as the average number with the first coordination shell. Full width at half maximum is given in parentheses.
Interface data. is geminal silanol. Full width at half maximum is given in parentheses.
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