立方晶系結(jié)構(gòu)的確定

立方晶系結(jié)構(gòu)確定方法內(nèi)容

基礎(chǔ)知識(shí)1計(jì)算原理2計(jì)算示例3基礎(chǔ)知識(shí)

完成未知晶體結(jié)構(gòu)的測(cè)定主要包括三個(gè)步驟：通過(guò)衍射峰的角度位置，計(jì)算單位晶胞的大小和形狀。通過(guò)單位晶胞的大小和形狀、樣品的化學(xué)組成和測(cè)定的密度，計(jì)算單位晶胞的原子數(shù)。通過(guò)衍射峰的相對(duì)強(qiáng)度，推斷出單位晶胞內(nèi)的原子位置。基礎(chǔ)知識(shí)立方晶體布拉維點(diǎn)陣參數(shù)簡(jiǎn)單立方B

c

c

(體心立方)F

c

c(面心立方)基礎(chǔ)知識(shí)晶格類型

hkl標(biāo)注原則消光條件

簡(jiǎn)單晶胞無(wú)要求無(wú)消光現(xiàn)象

Bcc

h+k+l為偶數(shù)h+k+l=奇數(shù)F

c

chkl全奇或全偶h、k、l奇偶混雜系統(tǒng)消光：由于原子在晶胞中位置不同或原子種類不同而導(dǎo)致某些衍射方向的強(qiáng)度減

弱或消失(為零)。計(jì)算原理（Bragg方程）（立方晶系晶面間距公式）計(jì)算原理傳統(tǒng)法分析法計(jì)算原理對(duì)于任何一個(gè)圖譜都是常數(shù)Why？計(jì)算示例2ThetaFig.1X-raydiffractionpatternofaluminun計(jì)算示例Peak#1234567892θ(o)38.5244.7665.1478.2682.4799.11112.03116.60137.47Sin2θ0.10880.14500.28980.39830.43450.57920.68760.72380.8684a(nm)0.404480.404570.404710.404800.404800.404850.404910.404910.404941.0001.3332.6643.6613.9945.3246.3206.6537.9823.0003.9997.99210.98311.98215.97218.96019.95823.945348111216192024111200220311222400331420422Al這個(gè)數(shù)值通常取2或3，選取的原則是：與

相乘后結(jié)果接近于整數(shù)取整計(jì)算示例Al3481112161920

24簡(jiǎn)單12345689101112131416bcc246810121416…fcc3481112161920242731…參比數(shù)據(jù)fcc結(jié)構(gòu)計(jì)算原理可能的值為1，2，3，4，5，6，8……求出共有的商計(jì)算示例Peak#1234567892θ(o)38.5244.7665.1478.2682.4799.11112.03116.60137.47Sin2θ0.10880.14500.28980.39830.43450.57920.68760.72380.86840.05440.07250.14490.19920.43420.36190.34380.28960.21730.01360.01810.03620.04980.05430.07240.08600.09050.10860.03630.04830.09660.13280.14480.19310.22920.24130.28950.02720.03630.07250.09960.10860.14480.17190.18100.21710.02180.02900.05800.07970.08690.11580.13750.14480.17370.01810.02420.04830.06640.07240.09650.11460.12060.1447AlA=0.036計(jì)算示例Peak#123456789Sin2θ0.10880.14500.28980.39830.43450.57920.68760.72380.86843481112161920241112002203112224003314204222.9973.9957.98310.97211.97015.95618.94219.93923.923A=0.036取整米勒指數(shù)是非混合的(都是奇數(shù)或都是偶數(shù))

驗(yàn)證了Al是fcc結(jié)構(gòu)計(jì)算示例A=0.0363

與前一種方法結(jié)果一致Thanksforyou