C..50 PW91X: Perdew-Wang 1991 GGA Exchange Functional

\begin{dmath}
g=1/2\,E \left( 2\,\rho \left( s \right) \right)
,\end{dmath}

\begin{dmath}
G=1/2\,E \left( 2\,\rho \left( s \right) \right)
,\end{dmath}

\begin{dmath}
E \left( n \right) =-3/4\,{\frac {\sqrt [3]{3}\sqrt [3]{{\pi }^{2}}{n}^
{4/3}F \left( S \right) }{\pi }}
,\end{dmath}

\begin{dmath}
S=1/12\,{\frac {\chi \left( s \right) {6}^{2/3}}{\sqrt [3]{{\pi }^{2}}}
}
,\end{dmath}

\begin{dmath}
F \left( S \right) ={\frac {1+ 0.19645\,S{\it arcsinh} \left( 7.79...
....19645\,S{\it arcsinh} \left( 7.7956\,S \right) + 0.004\,{S}^{4}
}}
.\end{dmath}



molpro@molpro.net 2018-10-21