In a recent work, the extremely anomalous mechanical behavior of the anhydrous zinc and cadmium oxalates was discovered. In this paper, the mechanical behavior of the anhydrous mercury oxalate containing the remaining transition metal element of the IIB group of periodic table is investigated. The crystal structure and elastic properties of \({\text{HgC}}_{2} {\text{O}}_{4}\) are determined using first-principles solid-state methods. Although the structure of mercury oxalate and the coordination environment of mercury in this compound are radically different to those of the zinc and cadmium oxalates, a great degree of similarity in their mechanical behavior is unexpectedly found. The mechanical behavior of mercury oxalate is anomalous and exhibits the negative Poisson’s ratio (NPR) and the negative linear compressibility (NLC) phenomena. Under isotropic pressure, the compressibility along the [1,0,0] crystallographic direction is negative in the pressure range from − 2.50 to 0.25 GPa. For external pressures applied in the direction of minimum compressibility, which coincides with [1,0,0], mercury oxalate exhibits negative volumetric compressibilities from 0.22 to 1.40 GPa. The increase in volume in this material is significant for pressures larger than 1.0 GPa, and the compressibility becomes − 95.6 \({\text{TPa}}^{ - 1}\) at P = 1.36 GPa. As for the zinc and cadmium oxalates, the increase in volume is so drastic that mercury oxalate becomes unstable for pressures larger than 1.4 GPa. The NLC effect in mercury oxalate is due to the highly deformable character of the cube coordination polyhedron of mercury. The coordination structure becomes octahedral near P = 1.3 GPa, just before its structural instability.

在最近的工作中，发现了无水锌和草酸镉的异常机械行为。本文研究了含有元素周期表中IIB族过渡金属元素的无水草酸汞的力学行为。\（{\ text {HgC}} _​​ {2} {\ text {O}} _ {4} \）的晶体结构和弹性性质使用第一原理固态方法确定。尽管该化合物中的草酸汞的结构和汞的配位环境与草酸锌和草酸镉的存在根本不同，但出乎意料地发现了它们在机械性能上的高度相似性。草酸汞的机械行为异常，并表现出负的泊松比（NPR）和负的线性可压缩性（NLC）现象。在各向同性压力下，沿着[1,0,0]结晶方向的可压缩性在-2.50至0.25 GPa的压力范围内为负。对于以最小可压缩性方向（与[1,0,0]一致）施加的外部压力，草酸汞表现出从0.22至1.40 GPa的负体积压缩率。\（{\ text {TPa}} ^ {-1} \）在P  = 1.36 GPa。至于草酸锌和镉，体积的增加是如此之大，以至于在压力大于1.4 GPa时草酸汞变得不稳定。草酸汞中的NLC效应归因于汞的立方配位多面体的高度可变形特性。 在结构不稳定之前，配位结构在P = 1.3 GPa附近变为八面体。