Title: Tetrahedrality, hydrogen bonding and the density anomaly of the central force water model. A Monte Carlo study
Author(s):

	V. Ravnik (Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia),
	B. Hribar-Lee (Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia),
	O. Pizio (Instituto de Química, Universidad Nacional Autonoma de México, Circuito Exterior, Ciudad Universitaria, 04510, Cd. de México, México),
	M.Lukšič (Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia)

Monte Carlo computer simulations in the canonical and grand canonical statistical ensemble were used to explore the properties of the central force (CF1) water model. The intramolecular structure of the H₂O molecule is well reproduced by the model. Emphasis was made on hydrogen bonding, and on the tehrahedral, q, and translational, τ, order parameters. An energetic definition of the hydrogen bond gives more consistent results for the average number of hydrogen bonds compared to the one-parameter distance criterion. At 300 K, an average value of 3.8 was obtained. The q and τ metrics were used to elucidate the water-like anomalous behaviour of the CF1 model. The structural anomalies lead to the density anomaly, with a good agreement of the model's density with the experimental ρ(T) trends. The chemical potential-density projection of the model's equation of state was explored. Vapour-liquid coexistence was observed at sufficiently low temperatures.

Key words: central force water model, hydrogen bonding, tetrahedraly, density anomaly, equation of state, Monte Carlo simulations

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