切换到宽版
  • 3249阅读
  • 3回复

关于CO2的原子晶体的疑问 [复制链接]

上一主题 下一主题
离线kio3
 

只看楼主 倒序阅读 楼主  发表于: 2010-09-21
     《Science》说高压下CO₂变成SiO₂型的原子晶体,变成原子晶体我没意见,不过是SiO₂型,我就觉得奇怪了。
       SiO₂的∠Si—O—Si=180°显然其中的O取sp杂化,还剩两个p轨道和Si的3d轨道形成d-pπ键。Si可以搞d-pπ键,C就不行了,原子晶体的CO₂中的O只能取sp³杂化。
       依我之见:原子晶体的CO₂取SiS₂型比取SiO₂型更为合理,至少键角正常点。不知各位有何意见?是《Science》误记,我的分析有错,还是理论不够完善?

氰负离子进攻羰基,生成α-羟基腈,后者简称清纯
离线Cosmology

只看该作者 沙发  发表于: 2010-09-21
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。
思维简单一点,爱情高尚一点,期待真诚一点,信念炽热一点,说话谦虚一点。
离线kio3

只看该作者 板凳  发表于: 2010-09-21
感谢Cosmology,SiO2的∠Si—O—Si不全是180°我是第一次知道。
《Science》没说∠C—O—C=180°,是我孤陋寡闻,只知道∠Si—O—Si的180°,于是推测的……
氰负离子进攻羰基,生成α-羟基腈,后者简称清纯
离线叶绿素

只看该作者 地板  发表于: 2010-09-22
路过长见识了
其实,我是化无机为有机的~~~~~
快速回复
限100 字节
如果您在写长篇帖子又不马上发表,建议存为草稿
 
上一个 下一个