\begin{table}%t14
%\centering
\par
\caption{\label{tab_mesh}The energy meshes (in unit of~$q^2$, residual charge of ion) used for each ion.} 
\par
\begin{tabular}{ccccc}
\hline\hline\noalign{\smallskip}
{\rm mesh} & \multicolumn{4}{c}{Atomic number}\\
\hline\noalign{\smallskip}
  $q^2${\rm Ryd}  & 11--14    & 15--17 &   18--30 &   31--36 \\
\hline\noalign{\smallskip}
$1\times10^{-4}$  & $\bullet$  &          &           &           \\
$5\times10^{-5}$  &            & $\bullet$  &           &           \\
$1\times10^{-5}$  &            & & $\bullet$   &           \\
$5\times10^{-6}$  &            & & & $\bullet$   \\
\hline
\end{tabular}
\end{table}