SPC/Fw model of water: Difference between revisions

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The '''SPC/Fw''' is a flexible variant of the rigid [[SPC]] model for [[water]]
The '''SPC/Fw''' is a flexible variant of the rigid [[SPC]] model for [[water]]
<ref>[http://dx.doi.org/10.1063/1.2136877 Yujie Wu, Harald L. Tepper and Gregory A. Voth "Flexible simple point-charge water model with improved liquid-state properties", Journal of Chemical Physics '''124''' 024503 (2006)]</ref>.
UNIQ2c14b0eded24b1ba-ref-00000023-QINU.
This model has also been re-parametrised for quantum simulations, adopting the name '''q-SPC/Fw'''  
This model has also been re-parametrised for quantum simulations, adopting the name '''q-SPC/Fw'''  
<ref name="q-SPC/Fw">[http://dx.doi.org/10.1063/1.2386157 Francesco Paesani, Wei Zhang, David A. Case, Thomas E. Cheatham, III and Gregory A. Voth "An accurate and simple quantum model for liquid water", Journal of Chemical Physics '''125''' 184507 (2006)]</ref>.  
UNIQ2c14b0eded24b1ba-ref-00000024-QINU.  
The model is given by the intra-molecular component (Eq. 2 of <ref name="q-SPC/Fw"> </ref>):
The model is given by the intra-molecular component (Eq. 2 of UNIQ2c14b0eded24b1ba-ref-00000025-QINU):


:<math>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  </math>
:UNIQ2c14b0eded24b1ba-math-00000026-QINU


and the inter-molecular component (Eq. 3 of <ref name="q-SPC/Fw"> </ref>):
and the inter-molecular component (Eq. 3 of UNIQ2c14b0eded24b1ba-ref-00000027-QINU):


:<math>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\} </math>
:UNIQ2c14b0eded24b1ba-math-00000028-QINU


The parameters for both of these models are given in the following table (Table I of <ref name="q-SPC/Fw"> </ref>):
The parameters for both of these models are given in the following table (Table I of UNIQ2c14b0eded24b1ba-ref-00000029-QINU):


[[Image:Thee_site_water_model.png‎|center|400px]]
[[Image:Thee_site_water_model.png‎|center|400px]]
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{| style="width:75%; height:100px" border="1"
{| style="width:75%; height:100px" border="1"
|-  
|-  
| Model  || <math>k_b</math> || <math>r^{\mathrm {eq}}_{\mathrm {OH}}</math> (&Aring;)|| <math>k_a</math> || <math>\vartheta^{\mathrm{eq}}_{\angle \mathrm{HOH}}</math> (deg)|| <math>\sigma_{\mathrm {OO}}</math> (&Aring;)|| <math>\epsilon_{\mathrm {OO}}</math> (kcal mol<sup>-1</sup>)|| q(O) (e) || q(H) (e)  
| Model  || UNIQ2c14b0eded24b1ba-math-0000002A-QINU || UNIQ2c14b0eded24b1ba-math-0000002B-QINU (&Aring;)|| UNIQ2c14b0eded24b1ba-math-0000002C-QINU || UNIQ2c14b0eded24b1ba-math-0000002D-QINU (deg)|| UNIQ2c14b0eded24b1ba-math-0000002E-QINU (&Aring;)|| UNIQ2c14b0eded24b1ba-math-0000002F-QINU (kcal mol<sup>-1</sup>)|| q(O) (e) || q(H) (e)  
|-  
|-  
| SPC/Fw || 1059.162    || 1.012 || 75.90 || 113.24 || 3.165492 || 0.1554253 || -0.82 || 0.41
| SPC/Fw || 1059.162    || 1.012 || 75.90 || 113.24 || 3.165492 || 0.1554253 || -0.82 || 0.41
Line 24: Line 24:
| q-SPC/Fw || 1059.162  || 1.000 || 75.90 || 112.0  || 3.165492 || 0.1554252 || -0.84 || 0.42
| q-SPC/Fw || 1059.162  || 1.000 || 75.90 || 112.0  || 3.165492 || 0.1554252 || -0.84 || 0.42
|}
|}
where the units of <math>k_b</math> and <math>k_a</math> are kcal.mol<sup>-1</sup>&Aring;<sup>-2</sup>.
where the units of UNIQ2c14b0eded24b1ba-math-00000030-QINU and UNIQ2c14b0eded24b1ba-math-00000031-QINU are kcal.mol<sup>-1</sup>&Aring;<sup>-2</sup> and  kcal.mol<sup>-1</sup>rad.<sup>-2</sup> respectively.
==Dielectric constant==
==Dielectric constant==
The dielectric constant has been calculated by  Raabe and  Sadus  <ref>[http://dx.doi.org/10.1063/1.3600337  Gabriele Raabe and Richard J. Sadus "Molecular dynamics simulation of the dielectric constant of water: The effect of bond flexibility", Journal of Chemical Physics '''134''' 234501 (2011)]</ref>.
The dielectric constant has been calculated by  Raabe and  Sadus  UNIQ2c14b0eded24b1ba-ref-00000032-QINU.
==References==
==References==
<references/>
UNIQ2c14b0eded24b1ba-references-00000033-QINU
{{numeric}}
{{numeric}}
[[category: water]]
[[category: water]]
[[category: models]]
[[category: models]]

Revision as of 00:04, 28 December 2014

The SPC/Fw is a flexible variant of the rigid SPC model for water ?UNIQ2c14b0eded24b1ba-ref-00000023-QINU?. This model has also been re-parametrised for quantum simulations, adopting the name q-SPC/Fw ?UNIQ2c14b0eded24b1ba-ref-00000024-QINU?. The model is given by the intra-molecular component (Eq. 2 of ?UNIQ2c14b0eded24b1ba-ref-00000025-QINU?):

?UNIQ2c14b0eded24b1ba-math-00000026-QINU?

and the inter-molecular component (Eq. 3 of ?UNIQ2c14b0eded24b1ba-ref-00000027-QINU?):

?UNIQ2c14b0eded24b1ba-math-00000028-QINU?

The parameters for both of these models are given in the following table (Table I of ?UNIQ2c14b0eded24b1ba-ref-00000029-QINU?):


Model ?UNIQ2c14b0eded24b1ba-math-0000002A-QINU? ?UNIQ2c14b0eded24b1ba-math-0000002B-QINU? (Å) ?UNIQ2c14b0eded24b1ba-math-0000002C-QINU? ?UNIQ2c14b0eded24b1ba-math-0000002D-QINU? (deg) ?UNIQ2c14b0eded24b1ba-math-0000002E-QINU? (Å) ?UNIQ2c14b0eded24b1ba-math-0000002F-QINU? (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 ?UNIQ2c14b0eded24b1ba-math-00000030-QINU? and ?UNIQ2c14b0eded24b1ba-math-00000031-QINU? are kcal.mol-1Å-2 and kcal.mol-1rad.-2 respectively.

Dielectric constant

The dielectric constant has been calculated by Raabe and Sadus ?UNIQ2c14b0eded24b1ba-ref-00000032-QINU?.

References

?UNIQ2c14b0eded24b1ba-references-00000033-QINU?

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