Sentence:  A randomization of `` ups '' and `` downs '' is more likely than ordered `` ups '' and `` downs '' in position ( 3 ) since the hydrogen atoms are well separated and so the position of one could hardly affect the position of another , and also since ordered `` up '' and `` down '' implies a larger <WSD>unit</WSD> cell , for which no evidence exists . 
Meaning of the word marked with <WSD> tags:  the smallest group of atoms or molecules whose repetition at regular intervals in three dimensions produces the lattices of a crystal