如何用 latex 编写簇积分？

Question

如何用乳胶生成下列方程式？

Answer 1

使用 Ti钾Z 绘制簇：

\documentclass[preview,border=3.14]{standalone}

\usepackage{tikz}
\usepackage[]{amsmath}

\tikzset
  {%
    ,cluster dif/.store in=\clusterDif
    ,cluster dif=.5
    ,cluster color/.store in=\clusterColor
    ,cluster color=blue
    ,cluster node/.style=%
      {%
        ,draw
        ,circle
        ,execute at begin node=$\scriptstyle
        ,execute at end node=$
        ,inner sep=1pt
      }%
  }

\newcommand\cluster[2][]
  {%
    \mathord
      {%
        \vcenter
          {%
            \hbox
              {%
                \tikz\draw[\clusterColor,#1] node[cluster node](1){1}
                  ++(\clusterDif,0) node[cluster node](2){2}
                  ++(-120:\clusterDif) node[cluster node](3){3}
                  \foreach\x/\y in {#2}{(\x)--(\y)}
                  ;%
              }%
          }%
      }%
  }

\begin{document}
\begin{equation}
  b_3(V,T) =
    \frac{1}{3!\,V}\int [\, \cluster{1/2,3/1} + \cluster{2/3} + \cluster{2/3,3/1} +
    \cluster{1/2,2/3,3/1} \,]
\end{equation}
\end{document}