Fig. 4
From: Carbon network evolution from dimers to sheets in superconducting ytrrium dicarbide under pressure
Pressure dependence of the structural order parameter in high-pressure phases of YC2. Through the Immm (YC2-IV) - P6/mmm (YC2-V) phase transition, upon compression, the lengths of two kinds of C-C bonds in the double chain of the YC2-IV phase gradually approach one another before a first-order transition to the sheet structure of YC2-V
