中文摘要：

本文通过实验观察和理论计算研究了金刚石单晶解理断裂现象。金刚石单晶晶面上实际的价电子密度并非简单的正比于原子密度。（110）晶面上原子分布不均匀。（110）晶面BQKJB区域内原子分布较少，原子密度低于其它晶面。（111）晶面的价电子键络分布均匀，且实际发生作用的价电子密度最大。计算和分析结果表明，金刚石单晶（111）晶面的有效价电子密度为46．212nm^-2，明显高于（110）晶面的38．542nm^-2，成为有效原子密排面。当金刚石受到外力作用时，（111）面间较弱的键相对更容易断裂，因而导致沿（111）面产生解理。这与实验观察结果相吻合。

英文摘要：

The fracture of diamond single crystal was studied through experimental observation .and calculation. It was observed that the actual valence electron density of crystal plane was not simply in direct proportion to that of atom. The distribution of atoms in the （110） plane was not uniform. There were a little atoms in BQKJB region of （110） plane, and its atom density was less than others. The valence electron bond of （ 111 ） plane was distributed uniformly, and the valence electron density acting to （ 111 ） plane was the biggest. The result of calculation and analysis indicated that the available valence electron density of （ 111 ） plane, 46.212 nm^-2, was higher than that of （110） plane which is 38. 542 nm^-2. And the （111） plane became the available atom close arrangement plane. Therefore, the cleavage of diamond maybe start from （ 111 ） plane. The conclusion is in good agreement with the result of experimental observation.