Section outline

  • General

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  • 金属晶体结构

    A cannon with wheels beside a pyramid stack of cannonballs for quick accessibility.

    How would you stack cannon balls?
    ::你会如何堆放大炮球?

    Before modern artillery with explosive shells, cannons were used to fire cannon balls at the enemy.  The soldiers operating the cannon needed to be able to get to the cannon balls quickly and efficiently.  An arrangement such as the pyramid worked well for the purpose.
    ::在使用爆炸炮弹的现代炮火之前,炮火被用来向敌人发射炮火炮弹,操作炮火的士兵必须能够迅速、高效地获得炮火炮弹,金字塔等安排对此起到了很好的作用。

    Crystal Structures of Metals
    ::金属晶体结构

    When identical spheres are stacked, each successive layer fits into the small spaces where different spheres come together.  This orderly and regular arrangement of the metal balls minimizes the empty space between them.  Closest packing is the most efficient arrangement of spheres.  Atoms of a metal crystal are arranged in similar patterns, called close-packed structures.  Pure adopt one of several related close-packed structures as shown below.
    ::当相同的球体堆叠时, 每一相继的层都适合不同球体聚集的较小空间。 这种金属球的有序和常规安排会将它们之间的空空间最小化。 最接近的包装是球体最有效的安排。 金属晶体的原子会以类似的方式排列, 称为近包装结构。 纯采用下面所示的若干相关近包装结构之一 。

    metal crystal structures: body-centered cubic, face-centered cubic, hexagonal close-packed.
    Most pure metals naturally adopt one of these three closest packing arrangements.

    In the Figure , the far left model represents a body-centered cubic (bcc) structure.  In that crystal, metal atoms occupy the eight corners of a cube along with one in the very center. The of each atom in the body-centered cubic structure is 8.  In the center, depicting a face-centered cubic (fcc) structure, there are eight atoms at each corner of the cube and six atoms in the center of each face. The coordination number of each atom in the face-centered cubic structure is 12.  The hexagonal close-packed (hcp) structure shown in the rightmost model also has a coordination number of 12, but crystals of this type are hexagonally shaped rather than cubic.
    ::在图中,远左模型代表一个以身体为中心的立方体(bcc)结构。在该晶体中,金属原子占据一个立方体的8个角和中间的一个。在以身体为中心的立方体结构中,每个原子有8个。在中间,显示一个以脸为中心的立方体(fcc)结构,立方体每个角有8个原子,在每一面的中心有6个原子。在以脸为中心的立方体结构中,每个原子的协调号是12个。在右方模型中显示的六角近包装(hcp)结构也有12个协调号,但这种类型的晶体是六角形的,而不是立方形的。

     

    Summary
    ::摘要

    • Atoms of a metal crystal are arranged in close-packed structures.
      ::金属晶体原子安排在近包装结构中。
    • This type of structure minimizes the empty space between the atoms.
      ::这种结构将原子之间的空位最小化 。

    Review
    ::回顾

    1. What is the most efficient arrangement of spheres?
      ::什么是最有效的领域安排?
    2. What is the coordination number of a face-centered cubic structure?
      ::面对面的立方体结构的协调编号是什么?
    3. What other structure has a coordination number of 12?
      ::有哪些其他机构的协调编号为12?