Agfdhyk

How can I improve brakets in this equation please?

begin{equation}label{E}

E_0^{(1)} = expval{frac{e'^2}{|vec{r_1}-vec{r_2}|}}{Phi}

end{equation}

EDIT:
And please, what is wrong here? I think that in the end should be {Phi }, but it is mistake by compilation.

documentclass{article}

usepackage{physics}

begin{document}

begin{equation}label{E}

E_0^{(1)} = 4 pi e'^2 expval**{frac{1}{|vec{r}_2|} sumlimits_{l=0}^{infty} sumlimits_{m=-l}^l left(frac{|vec{x}^{(1)}|}{|vec{x}^{(2)}|} right)^l Phi }\

end{equation}

end{document}

If you're using the physics package, then it looks like you have to pass two * arguments to expval to allow it to auto-resize the brackets.

As for your second equation, it is missing an argument. You had expval**{stuff Phi}, but you need to provide another argument: expval**{stuff}{Phi}.

documentclass{article}

usepackage{physics}

begin{document}

begin{equation}label{E}

E_0^{(1)} = expval**{frac{e'^2}{|vec{r}_1-vec{r}_2|}}{Phi}

end{equation}

begin{equation}label{E2}

E_0^{(1)} = 4 pi e'^2 expval**{frac{1}{|vec{r}_2|} sum_{l=0}^infty sum_{m=-l}^l left(frac{|vec{x}^{(1)}|}{|vec{x}^{(2)}|} right)^l}{Phi}

end{equation}

end{document}

I do not know where expval comes from but with braket you could do

documentclass{article}

usepackage{amsmath}

usepackage{braket}

begin{document}

begin{equation}label{E}

E_0^{(1)} = Braket{Phi | frac{e'^2}{left|vec r_1 - vec r_2right|} | Phi}

end{equation}

end{document}