Covalent bonding in silicon.
<a href="//commons.wikimedia.org/wiki/User:%D0%94.%D0%98%D0%BB%D1%8C%D0%B8%D0%BD" title="User:Д.Ильин">Д.Ильин</a>: translation, optimization
<bdi><a href="https://www.wikidata.org/wiki/Q81411358" class="extiw" title="d:Q81411358"><span title="academic researcher in electronics engineering, a university professor in France, and activist in the Wikimedia movement">Michel Bakni</span></a>
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