石墨是一种混合晶体
在石墨晶体中,同层的碳原子以sp2杂化形成共价键,每一个碳原子以三个共价键与另外三个原子相连。六个碳原子在同一个平面上形成了正六连连形的环,伸展成片层结构,这里C-C键的键长皆为142pm,这正好属于原子晶体的键长范围,因此对于同一层来说,它是原子晶体。在同一平面的碳原子还各剩下一个p轨道,它们相互重叠。电子比较自由,相当于金属中的自由电子,所以石墨能导热和导电,这正是金属晶体特征。因此也归类于金属晶体。
In graphite crystals, carbon atoms in the same layer form covalent bonds by SP2 hybridization, and each carbon atom is connected with the other three atoms by three covalent bonds. Six carbon atoms form a hexagonal ring on the same plane, stretching into a lamellar structure, where the bond length of C-C bond is 142pm, which belongs to the bond length range of atomic crystals, so it is an atomic crystal in the same layer. Carbon atoms in the same plane have one p orbital each, and they overlap with each other. Electrons are relatively free, equivalent to free electrons in metal, so graphite can conduct heat and electricity, which is the characteristics of metal crystal. Therefore, it is also classified as metallic crystal.
石墨晶体中层与层之间相隔340pm,距离较大,是以范德华力结合起来的,即层与层之间属于分子晶体。但是,由于同一平面层上的碳原子间结合很强,极难破坏,所以石墨的熔点也很高,化学性质也稳定。
The middle layer of graphite crystal is 340 PM apart from the layer, and the distance is large. It is combined by van der Waals force. That is to say, the layer belongs to molecular crystal. However, due to the strong bonding between carbon atoms in the same plane layer, it is extremely difficult to destroy, so the melting point of graphite is very high, and its chemical properties are stable.
鉴于它的特殊的成键方式,不能单一的认为是单晶体或者是多晶体,按现代的表述方式,认为石墨是一种混合晶体。
In view of its special bonding mode, graphite can not be regarded as single crystal or polycrystal. According to modern expression, graphite is considered as a mixed crystal.