6

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}

enter image description here

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|} \sum\limits_{l=0}^{\infty} \sum\limits_{m=-l}^l \left(\frac{|\vec{x}^{(1)}|}{|\vec{x}^{(2)}|} \right)^l \Phi }\\
\end{equation}
\end{document}
4
  • 3
    \left...\right? P.S. I usually write \vec{r}_1 because of space.
    – manooooh
    Nov 9, 2018 at 19:36
  • 4
    Please provide a compilable example. Where does the \expval command come from? Nov 9, 2018 at 19:37
  • 1
    Off-topic: One should probably write \vec{r}_1 instead of \vec{r_1}, and \vec{r}_2 instead of \vec{r_2}.
    – Mico
    Nov 9, 2018 at 20:04
  • 1
    Instead of editing an existing query to pose what's essentially a new question, you should post a new query.
    – Mico
    Nov 9, 2018 at 20:07

2 Answers 2

8

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}

enter image description here

4
  • Please, can I have one more question - I editted my origin question.
    – Elisabeth
    Nov 9, 2018 at 20:08
  • 1
    @Elisabeth The solution was simple, so I also updated my answer. If you happen to have more problems it's advisable, as Mico said, to ask a new question instead of editing an old question. Nov 9, 2018 at 20:10
  • You should definitely remove the double-backslash stuff at the end of the equation environments. Also, the \limits directives are redundant; all they do is create code clutter.
    – Mico
    Nov 9, 2018 at 20:12
  • 1
    @Mico Oops, I forgot those there. Thanks for pointing it out :-) Nov 9, 2018 at 20:15
9

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_2\right|} | \Phi}
\end{equation}
\end{document}

enter image description here

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