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 ):

$V^{\mathrm {intra} }={\frac {k_{b}}{2}}\left[\left(r_{\mathrm {OH} _{1}}-r_{\mathrm {OH} }^{\mathrm {eq} }\right)^{2}+\left(r_{\mathrm {OH} _{2}}-r_{\mathrm {OH} }^{\mathrm {eq} }\right)^{2}\right]+{\frac {k_{a}}{2}}\left(\vartheta _{\angle \mathrm {HOH} }-\vartheta _{\angle \mathrm {HOH} }^{\mathrm {eq} }\right)^{2}$

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	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}	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}	$\vartheta _{\angle \mathrm {HOH} }^{\mathrm {eq} }$ (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)	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 \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 .