We present ab initio studies of possible reconstruction elements on Si and $\text{Ge}\left(110\right)$ surfaces. Using $2\times 2$, $3\times 2$, and $6\times 2$ unit cells we optimize models with buckled atomic chains, dimers, different adatom distributions, and interstitial atoms which may exist on the larger $\text{Si}\left(110\right)16\times 2$ or $\text{Ge}\left(110\right)16\times 2∕c\left(8\times 10\right)$ surface reconstructions. We show that adatom reconstructions gain energy. Only the adatom model which seemingly leaves no dangling bonds cannot occur on Si and $\text{Ge}\left(110\right)$ surfaces. An adatom-rest atom electron transfer mechanism is more favorable. An adatom-tetramer-interstitial $3\times 2$ model also stabilizes the Si and Ge surfaces and leads to a semiconducting behavior (at least for Si). Simulated scanning tunneling microscopy (STM) images of empty states of this reconstruction look like the pentagon structures observed on $\text{Si}\left(110\right)16\times 2$. A $6\times 2$ reconstruction with five-membered adclusters is energetically completely unfavorable, though it also reproduces the empty-state pentagonlike STM images.

• Received 2 December 2003

DOI:https://doi.org/10.1103/PhysRevB.70.045305