晶胞参数的测定优秀PPT.ppt

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1、晶胞参数的测定你现在浏览的是第一页，共19页OutlineExperimental Goal1.Background and Theory2.Example3.你现在浏览的是第二页，共19页Experimental Goal Determine the precise lattice parameters of materials你现在浏览的是第三页，共19页Background and TheoryImportance Useful in determining solid solubility limits of one component in another,coefficients

2、of thermal expansion,and true densities of materials.The magnitudes of changes in the lattice parameters due to a change in solute content or temperature are so small.你现在浏览的是第四页，共19页Background and TheoryA material with a cubic structure你现在浏览的是第五页，共19页Background and TheoryMethodsDebye-Scherrer Camera

3、sDiffractometersMathematizationExtrapolation Debye-Scherrer Cameras Bradley-Jay Nelson-Riley Diffractometers The least-square method你现在浏览的是第六页，共19页Background and TheoryDebye-Scherrer CamerasSources of error:Film shrinkage Incorrect camera radius Off-centering of specimen Absorption in specimen Diver

4、gence of the beam你现在浏览的是第七页，共19页Background and TheoryDiffractometersSources of error:Misalignment of the instrument Use of a flat specimen instead of a specimen curved to conform to the focusing circle Absorption in the specimen Displacement of the specimen from the diffractometer axis Vertical dive

5、rgence of the incident beam你现在浏览的是第八页，共19页Background and TheoryExtrapolation1.Since varies differently with different errors，a single extrapolation function is not satisfactory in this case2.It is necessary to have as many reflections as possible in the high-angle region of the diffraction pattern s

6、o that you will have many Pointsenabling you to draw the best possible straight line你现在浏览的是第九页，共19页Background and TheoryThe least-square methodNormal Equations Drift constant你现在浏览的是第十页，共19页ExampleFIG 1X-ray diffraction pattern of aluminum showing only the high-angle regionThe least-square method-Alu

7、minum你现在浏览的是第十一页，共19页ExampleTable 1 Calculation of the Lattice Parameter of Aluminum你现在浏览的是第十二页，共19页ExampleTABLE 2 Data Required for Cohens Analytical Method你现在浏览的是第十三页，共19页Example 2674A+858.9C=96.77139858.9A+313.14C=31.08341A=0.0361895 C=7.810-7 你现在浏览的是第十四页，共19页ExampleFIG2 X-ray diffraction pattern

8、 of silicon showing only the highangle regionExtrapolation-Silicon你现在浏览的是第十五页，共19页ExampleTABLE 3 Work Table for Indexing the Diffraction Pattern of Silicon你现在浏览的是第十六页，共19页Examplea0=0.5430nmTrue value a0=0.5431 nmFIG 3 The straight line by extrapolating lattice parameters against 你现在浏览的是第十七页，共19页Examplea0=0.5430nmTrue value a0=0.5431 nmFIG 4 The straight line by extrapolating lattice parameters against 你现在浏览的是第十八页，共19页你现在浏览的是第十九页，共19页