Type-setting quadruple bonds in LaTeX

Question

How does one typeset quadruple bonds in LaTeX? I've tried several things: Vertically stacking equal signs, putting lines in tables, etc.

Single up to tripple bonds is easy (by using the chemfig package, https://www.sharelatex.com/learn/Chemistry_formulae), but quadruple bonds seem to be different.

I've created a "quadruple bond" this way:

 \begin{table}
\resizebox{5mm}{!}{
\begin{tabular}{c}
 \rule[0mm]{22mm}{1pt} \\
 \rule[0mm]{22mm}{1pt} \\
  \rule[0mm]{22mm}{1pt} \\
  \rule[0mm]{22mm}{1pt}
\end{tabular}
}
\end{table}

Still trying to figure a way of placing it in-line..

Answer 1

If, as per your comment, you just want to draw the bond as part of a line of text, I’d go straight for the Tikz that underlies chemfig:

\newcommand{\quadruplebond}[2]{
  \begin{tikzpicture}[x=3em, y=0.2ex]
    \node (a1) at (0,0) {#1}; 
    \node (a2) at (1,0) {#2};
    \foreach \i in {-3,-1,1,3} {
      \path (a2.west) +(0,\i) node[coordinate] (t\i) {};
      \draw (a1.east) +(0,\i) -- (t\i);
    }
  \end{tikzpicture}
}

will allow you to write \quadruplebond{Ti}{Ti} and get . Change the x and y values to adjust the bond length and spacing. This is not the most sophisticated code imaginable but will at least scale with text sizes.

(To use this code in general you will need \usepackage{tikz}, but if you are already loading chemfig this will have been done for you.)

Answer 2

Here is another way to achieve quadruple bonds:

\documentclass{article}
\usepackage{chemfig}
\def\fourbondsep{1pt}
\usetikzlibrary{decorations}
\pgfdeclaredecoration{ddddb}{initial}{
    \state{initial}[width=\pgfdecoratedremainingdistance]
        {\foreach\i in{1.5,0.5,-0.5,-1.5}{%
            \pgfpathmoveto{\pgfpoint{0pt}{\i*\fourbondsep}}\pgfpathlineto{\pgfpoint{\pgfdecoratedremainingdistance}{\i*\fourbondsep}}}
        }
    \state{final}
        {}
}
\tikzset{4bond/.style={decorate,decoration=ddddb}}
\begin{document}
\chemfig{Ti-[,,,,4bond]Ti}
\end{document}

Answer 3

If you want this for an inline formula I suggest using chemformula which easily allows you to define a new bond type. As explained in the manual this uses TikZ and the nodes (chemformula-bond-start) and (chemformula-bond-end). Here is an example for a possible quadruple bond definition:

\NewChemBond{quadruple}{
  \foreach \i in {-.15em,-.05em,.05em,.15em}{
    \draw[chembond]
      ([yshift=\i]chemformula-bond-start) -- ([yshift=\i]chemformula-bond-end) ;
  }
}

One can then use \bond{quadruple} in chemformula's \ch for the bond (\ch{Ti\bond{quadruple}Ti}). For convenience it is also possible to add a replacement symbol for the bond, especially when that bond is going to be used more than once:

\NewChemCompoundProperty{\#}{\bond{quadruple}}

Then this symbol can be used instead (\ch{Ti\#Ti}) for getting the quadruple bond.

A complete example:

\documentclass{article}
\usepackage{chemformula}
% define the bond:
\NewChemBond{quadruple}{
  \foreach \i in {-.15em,-.05em,.05em,.15em}{
    \draw[chembond]
      ([yshift=\i]chemformula-bond-start) -- ([yshift=\i]chemformula-bond-end) ;
  }
}
% define the replacement symbol for the new bond:
\NewChemCompoundProperty{\#}{\bond{quadruple}}

\begin{document}

\ch{Ti\bond{quadruple}Ti}

\ch{Ti\#Ti}

\end{document}