材料科學(xué)基礎(chǔ)(清華大學(xué))(存儲(chǔ)版)
【正文】 216。How to distinguish the size and shape of the deferent unit cell ? The six variables , which are described by lattice constants —— a , b , c 。Cubic a＝ b＝ c ， α＝ β＝ γ＝ 90176。 )3 Orthorhombic √ √ or √ or√ √ √4 Tetragonal √ √5 Cubic √ √ √6 Hexagonal √7 Rhombohedral √Seven crystal systems and fourteen lattice typesuⅢ.Primitive CellFor primitive cell, the volume is minimumPrimitive cellOnly includes one lattice pointuⅣ . Complex LatticeThe example of plex lattice120o120o120oExamples and Discussions1. Why are there only 14 space lattices?l Explain why there is no base centered and face centered tetragonal Bravais lattice.P → C I → FBut the volume is not minimum.2. Criterion for choice of unit cell? Symmetry? As many right angle as possible? The size of unit cell should be as small as possibleExercise1. Determine the number of lattice points per cell in the cubic crystal systems. If there is only one atom located at each lattice point, calculate the nu
環(huán)評(píng)公示相關(guān)推薦
鄂ICP備17016276號(hào)-1