[Tex/LaTex] Closing bracket and parenthesis in multline

Question

Where is an issue in my MWE with brackets when I split equation into two lines?

\documentclass[12pt, a4paper]{book}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\begin{document}



\begin{multline}
\chi(bt)=\frac{1}{\surd\bar{\pi}}\sum_{j=1}^{\infty}(-1)^{j+1}
\frac{(\surd\bar{\pi}^{j})}{\surd\overline{(j-1)!}}
exp\left[\left(-\frac{j\alpha n_{\alpha}F}{RT}\right)
\left(E-E^{0}+\frac{RT}{\alpha n_{\alpha}F}ln
\frac{\surd\overline{\pi Db}}{k_{s}}- \right. \nonumber \\
&\left. {} -\frac{RT}{\alpha n_{\alpha}F}ln\frac{K}{1+K}\right]
\end{multline}

\end{document}

The issue is that in the second line I get ] at the end but not ).

Answer 1

The simplest is to do a manual size adjustment for delimiters, with \biggl and \biggr.

I propose also another layout for the equation, which makes easier to read, in my opinion. However, you may have constraints I'm not aware of…

\documentclass[12pt, a4paper]{book}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{showframe}

\begin{document}

\begin{multline*}
  \chi(bt)=\frac{1}{\surd\bar{\pi}}\sum_{j=1}^{\infty}(-1)^{j+1}
  \frac{(\surd\bar{\pi}^{j})}{\surd\overline{(j-1)!}}
  \exp\left[-\frac{j\alpha n_{\alpha}F}{RT}
    \biggl(E-E^{0}+{}\right. \\ + \frac{RT}{\alpha n_{\alpha}F}\ln
    \frac{\surd\overline{\pi Db}}{k_{s}}
  \left.\left. {} -\frac{RT}{\alpha n_{\alpha}F}\ln\frac{K}{1+K}\right)\right]
\end{multline*}

\[
  \chi(bt)=\!\begin{aligned}[t]\frac{1}{\sqrt{\pi}}\sum_{j=1}^{\infty}(-1)^{j+1}
  \sqrt{\frac{\pi^j}{(j-1)!}}
  \exp j\biggl(\frac{\alpha n_{\alpha}F}{RT}
  (E^{0}-E) & - \ln
  \frac{\sqrt{\pi Db}}{k_{s}}\\[-1ex]
  & + \ln\frac{K}{1+K}\biggr)
  \end{aligned} \]

\end{document}