SPC/Fw model of water

The SPC/Fw is a flexible variant of the rigid SPC model for water . This model has also been re-parametrised for quantum simulations, adopting the name q-SPC/Fw . The model is given by the intra-molecular component (Eq. 2 of ):

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle V^{\mathrm {intra}} = \frac{k_b}{2} \left[ \left( r_{\mathrm {OH}_1} - r_{\mathrm {OH}}^{\mathrm {eq}} \right)^2 + \left( r_{\mathrm {OH}_2} - r_{\mathrm {OH}}^{\mathrm {eq}} \right)^2\right] + \frac{k_a}{2} \left( \vartheta_{\angle \mathrm{HOH}} - \vartheta^{\mathrm{eq}}_{\angle \mathrm{HOH}} \right)^2 }

and the inter-molecular component (Eq. 3 of ):

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle V^{\mathrm {inter}} = \sum_{ij}^{\mathrm{all~pairs}} \left\{ 4 \epsilon_{ij} \left[ \left(\frac{\sigma_{ij}}{R_{ij}} \right)^{12}- \left( \frac{\sigma_{ij}}{R_{ij}}\right)^6 \right] + \frac{q_i q_j}{R_{ij}}\right\} }

The parameters for both of these models are given in the following table (Table I of ):

Model	$k_{b}$	Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle r^{\mathrm {eq}}_{\mathrm {OH}}} (Å)	Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle k_a}	Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \vartheta^{\mathrm{eq}}_{\angle \mathrm{HOH}}} (deg)	Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \sigma_{\mathrm {OO}}} (Å)	$\epsilon _{\mathrm {OO} }$ (kcal mol-1)	q(O) (e)	q(H) (e)
SPC/Fw	1059.162	1.012	75.90	113.24	3.165492	0.1554253	-0.82	0.41
q-SPC/Fw	1059.162	1.000	75.90	112.0	3.165492	0.1554252	-0.84	0.42

where the units of Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle k_b} and Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle k_a} are kcal.mol^-1Å^-2.

Dielectric constant

The dielectric constant has been calculated by Raabe and Sadus .