# Greater bond distance for silicon diamond structure than for carbon diamond structure?

In the silicon diamond structure the bond distance is about two times the bond distance of the carbon diamond structure. Is this caused only by the greater dimension of $\mathrm{Si}$ atoms with respect to $\mathrm{C}$ atoms? Or are there other reasons for a greater bond distance in the case of silicon?

• How could you conclude that is not? It is tricky to isolate bond length from atom size. Jan 2 '18 at 15:37

\begin{align} d(\ce{C-C}) &= \pu{1.54 Å} \\ d(\ce{Si-Si}) &= \pu{2.35 Å} \\ \frac{d(\ce{Si-Si})}{d(\ce{C-C})} &\approx 1.53 \end{align}
\begin{align} r_\mathrm{cov}(\ce{C}) &= \pu{0.76 Å} \\ r_\mathrm{cov}(\ce{Si}) &= \pu{1.11 Å} \\ \frac{r_\mathrm{cov}(\ce{Si})}{r_\mathrm{cov}(\ce{C})} &\approx 1.46 \end{align}