你确定Science 上说高压下CO₂中C-O-C 的键角是180度了吗? SiO₂有很多晶型的,绝大部分Si-O-Si 的键角(比如常见的石英)都不是180度,只有磷石英Si-O-Si 的键角是180度。
这是我查到的,
http://www.esrf.eu/UsersAndScience/Publications/Highlights/1999/chemistry/polyco2.html"above 35 GPa and 1800 K, highly strained CO2-III transforms into a new phase CO2-V that can be quenched at ambient temperature (Figure 39c). It clearly shows that the texture in the transformed area is distinct from that in a non-transformed area. In this study, the crystal structure of CO2-V has been found to be orthorhombic (P212121), analogous to SiO2 tridymite (a distorted high temperature phase of ß-quartz). Each carbon atom is bonded to four oxygen atoms at a carbon-oxygen distance of 1.36 Å at 40 GPa and an O-C-O angle of 110°. These CO4 tetrahedral units share their corner oxygen atoms to form a layered structure in the ab-plane; whereas, the apices of the tetrahedra are connected through oxygen atoms along the c-axis (Figure 40). This interconnected layer structure of tetrahedra results in a C-O-C angle of 130°, substantially smaller than those of SiO2 tridymites 174-180° or of quartz 145°. Such rigidity in the C-O-C angles may reflect the fact that oxygen atoms in CO2-V are more tightly bound than in SiO2 and result in a higher covalence and bulk modulus for CO2-V than for any of the SiO2 polymorphs. In fact, we found that the bulk modulus of CO2-V is about 362 GPa, substantially higher than SiO2-quartz (37 GPa) and even stishovite (310 GPa). It is nearly the same value with cubic-BN (369 GPa) and thus could be a good candidate for a superhard polymer."
大意是说,30GPa 高压下,CO2 的晶型与磷石英类似,但C-O-C 的键角是130度,显著地比Si-O-Si 在磷石英(174度~180度)以及石英(145度)的键角小。