Principle of lattice parameter determination a 2dsin0=元 d= VH2+K2+D 几 a= VH2+K2+2 2sine △a △d a d
Principle of lattice parameter determination 2 2 2 2sin a H K L 2 d sin 2 2 2 H K L a d d d a a
The error in peak position determination 九 d 2sin 0 △兄 λ△0cosB △d= 2sin0 2sin20 △d △元△0cos0 d 元 sinθ
The error in peak position determination 2 2sin cos 2sin d 2sin d sin cos d d
1.0 业 不 △sin0 0.8 0 uls 0.6 △0→ 0.4- 0.2- 0.0 0 20 40 60 80 0(degrees) △d △元 △0cos0 The fractional error approaches d λ sinO zero as 0 approaches 90o
sin cos d d The fractional error approaches zero as approaches 90 o
Use peaks with large 20 0.030 0.025 0.05°-9 0.01°-A9 8 0.020 0.015 0.005°-9 p/pV 0.010 0.005 0.001°-A9 0.000 30405060708090 0() 点阵参数测量精度与和△的关系
30 40 50 60 70 80 90 0.000 0.005 0.010 0.015 0.020 0.025 0.030 d/d , % 0.010 ~ 0.050 ~ 0.0050 ~ 0.0010 ~ 点阵参数测量精度与 θ 和Δθ的关系 Use peaks with large 2
The key to high precision in parameter measurements lies in the use of back reflected beams having 20 values as near to 180 as possible! It is impossible to reach 180!