Negative volumetric thermal expansion for proposed hinged phases

Negative volumetric thermal expansion coefficients are predicted by molecular dynamics calculations for members of a broad family of materials based on three-connected, three-dimensional networks. This unusual feature, as well as novel mechanical properties, is a result of a soft shear deformation mode resulting from rotations about parallel bonds that serve as hinges. The investigated hinged phases include carbon and hydrocarbon phases based on polyacetylene and polyacene chains and on graphite sheets.