Sentence:  However , any <WSD>oxygen</WSD> nonequivalence would shorten either the already extremely short **f interlayer distance of 2.55 A or the non hydrogen bonded **f interlayer interactions which are already quite short at 2.58 A . 
Meaning of the word marked with <WSD> tags:  a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust