\begin{figure}[bhpt]
%\hspace{-40.pt}
\begin{minipage}[b]{0.5 \textwidth}
\includegraphics[width=\textwidth]{Fig.3(a).eps}
\caption{(a)}
\end{minipage}
\hspace{-0.2in}
\begin{minipage}[b]{0.5 \textwidth}
\includegraphics[width=\textwidth]{Fig.3(b).eps}
\caption{(b)}
\end{minipage}
\hspace{-40.0pt}
\par \vspace{-10.pt}
\hspace{-36.0pt}
\begin{minipage}[b]{0.5 \textwidth}
\includegraphics[width=\textwidth]{kongbai.eps}
\caption{(c)}
\end{minipage}
\hspace{-0.2in}
\begin{minipage}[b]{0.5 \textwidth}
\includegraphics[width=\textwidth]{Fig.3(d).eps}
\caption{(d)}
\end{minipage}
\hspace{-40.0pt}
\par \vspace{-10.pt}
\hspace{-36.0pt}
\begin{minipage}[b]{0.5 \textwidth}
\includegraphics[width=\textwidth]{Fig.3(e).eps}
\caption{(e)}
\end{minipage}
\hspace{-0.2in}
\begin{minipage}[b]{0.5 \textwidth}
\includegraphics[width=\textwidth]{Fig.3(f).eps}
\caption{(f)}
\end{minipage}
%\hspace{-40.0pt} \label{Fig.4}\caption{ Calculated density}
\end{figure}
\clearpage