Vega equation of state for hard ellipsoids

The Vega equation of state for an isotropic fluid of hard (biaxial) ellipsoids is given by (Eq. 20):

$Z=1+B_{2}^{*}y+B_{3}^{*}y^{2}+B_{4}^{*}y^{3}+B_{5}^{*}y^{4}+{\frac {B_{2}}{4}}\left({\frac {1+y+y^{2}-y^{3}}{(1-y)^{3}}}-1-4y-10y^{2}-18.3648y^{3}-28.2245y^{4}\right)$

where $Z$ is the compressibility factor and $y$ is the volume fraction, given by $y=\rho V$ where $\rho$ is the number density. The virial coefficients are given by the fits

$B_{3}^{*}=10+13.094756\alpha '-2.073909\tau '+4.096689\alpha '^{2}+2.325342\tau '^{2}-5.791266\alpha '\tau ',$

$B_{4}^{*}=18.3648+27.714434\alpha '-10.2046\tau '+11.142963\alpha '^{2}+8.634491\tau '^{2}-28.279451\alpha '\tau '-17.190946\alpha '^{2}\tau '+24.188979\alpha '\tau '^{2}+0.74674\alpha '^{3}-9.455150\tau '^{3},$

and

$B_{5}^{*}=28.2245+21.288105\alpha '+4.525788\tau '+36.032793\alpha '^{2}+59.0098\tau '^{2}-118.407497\alpha '\tau '+24.164622\alpha '^{2}\tau '+139.766174\alpha '\tau '^{2}-50.490244\alpha '^{3}-120.995139\tau '^{3}+12.624655\alpha '^{3}\tau ',$

where

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 B_n^*= B_n/V^{n-1}} ,

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 \tau' = \frac{4 \pi R^2}{S} -1,}

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 \alpha' = \frac{RS}{3V}-1.}

where 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} is the volume, $S$, the surface area, 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 R} the mean radius of curvature. These can be calculated using this Mathematica notebook file for calculating the surface area and mean radius of curvature of an ellipsoid. For 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 B_2} see the page "Second virial coefficient".

References

Related reading

• Carl McBride and Enrique Lomba "Hard biaxial ellipsoids revisited: Numerical results", Fluid Phase Equilibria 255 pp. 37-45 (2007)