Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2011 Sep 7;133(35):13840-3. doi: 10.1021/ja204971n. Epub 2011 Aug 15.
The family of materials RE(4)TGe(8) (RE = Yb, Gd; T = transition metal) exhibits directional zero thermal expansion (ZTE) via a process that is associated with the linking of planar square nets in the third dimension. The Ge square nets in these compounds exhibit commensurate long-range modulations similar to those observed in charge-density-wave compounds. The ZTE is manifested in the plane of the square nets from 10 to 300 K with negligible volume expansion below ∼160 K. The specific atomic arrangement in RE(4)TGe(8) enables a Poisson-like mechanism that allows the structure to contract along one direction as it expands only slightly in the perpendicular direction.
RE(4)TGe(8)（RE = Yb，Gd；T = 过渡金属）系列材料通过与第三维中平面正方形网的连接实现了各向同性零热膨胀（ZTE）。这些化合物中的 Ge 正方形网表现出类似于电荷密度波化合物中观察到的相匹配的长程调制。ZTE 在 10 至 300 K 的正方形网平面上表现出来，在约 160 K 以下几乎没有体积膨胀。RE(4)TGe(8)中的特定原子排列方式使结构能够沿一个方向收缩，同时仅在垂直方向上略有膨胀，这类似于泊松效应。
