\documentclass[12pt,a4paper,twocolumn]{article}


\usepackage{tabu}
\usepackage{booktabs}% for better rules in the table

%\usepackage{xepersian}
%\settextfont{B Nazanin}
%\DefaultMathsDigits

\begin{document}
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\begin{table}[h]\scriptsize
\begin{tabu} to .5\textwidth {XXXXX}
   \toprule
$\lambda_1$ & $Cluster 1$ &  & $Cluster 2$ &  \\
   & $Non migrative$ & $Migrative$  & $Non migrative$ & $migrative$ \\
\hline
2.6 & 0.55 & 0.60 & 0.64 & 0.62 \\
2.7 & 0.57 & 0.62 & 0.66 & o.64 \\
2.8 & 0.60 & 0.64 & 0.69 & 0.67 \\
2.9 & 0.62 & 0.66 & 0.70 & 0.69 \\
   \bottomrule
\end{tabu}
\end{table}


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\end{document}