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Published byDouglas Marshall Modified over 9 years ago
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Simulated diffraction image simulatedreal
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SimulatedstatisticReal 5.4%R merge 6.2% 18.9I/sd16.2 1.9I/sd (1.4 Ǻ)1.6 1.7 4.0 0.020SDCORR1.0 2.2 0.065 36.8PADFPH31.46 3.871mlphare f”3.476 0.178FOM0.192 0.545FOMDM0.664 0.6270CC(1H87)0.6090 0.170R cryst 0.184 0.205R free 0.231
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Program flow overview ano_sfall.com mlfsom.com hkl2XYphi.awk mapman
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d = (r 2 +g 2 ) 1/2 Point Spread Function I ~ Ω = g(r 2 +g 2 ) -3/2 g r Ω = g/d 3
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Point Spread Function pixel intensity (ADU) distance from “point” (mm) 10 7 10 6 10 5 10 4 10 3 100 10 1 0.01 0.1 1 2 re-sampled sum scaled and shifted I ~ g(r 2 +g 2 ) -3/2 g = 30 μm
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Darwin’s Formula I(hkl)- photons/spot (fully-recorded) I beam - incident (photons/s/m 2 ) r e - classical electron radius (2.818x10 -15 m) V xtal - volume of crystal (in m 3 ) V cell - volume of unit cell (in m 3 ) λ- x-ray wavelength (in meters!) ω- rotation speed (radians/s) L- Lorentz factor (speed/speed) P- polarization factor (1+cos 2 (2θ) -Pfac∙cos(2Φ)sin 2 (2θ))/2 A- absorption factor exp(-μ xtal ∙l path ) F(hkl)- structure amplitude (electrons) C. G. Darwin (1914) P A | F(hkl) | 2 I(hkl) = I beam r e 2 V xtal V cell λ 3 L ωV cell
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Background scattering I bg - scattered photons/steradian I beam - incident (photons/s/m 2 ) t- exposure time (s) r e - classical electron radius (2.818x10 -15 m) N A - Avogadro number (6.02x10 23 ) ρ- density of material (g/m 3 ) Mr- molecular weight (g/mol) V- volume of material (in m3) P- polarization factor (1+cos 2 (2θ) -Pfac∙cos(2Φ)sin 2 (2θ))/2 A- absorption factor exp(-μ xtal ∙l path ) f(s)- molecular structure amplitude (electrons) s- scattering length (sin(θ)/λ) P A | f(s) | 2 I bg = I beam t r e 2 N A ρV Mr R. W. James (1947)
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Background scattering Resolution (Ǻ) Photons/s/pixel Se edge with detector at 100 mm 7.5 3.8 2.5 1.9 1.5 1.2 1.1
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Diffuse scattering I ds - scattered photons/steradian I beam - incident (photons/s/m 2 ) t- exposure time (s) r e - classical electron radius (2.818x10 -15 m) V xtal - volume of crystal (in m 3 ) V ASU - asymmetric unit (in m 3 ) P- polarization factor A- absorption factor a- particular atom in the ASU f a (s)- atomic structure amplitude (electrons) s- scattering length (sin(θ)/λ) B a - atomic B factor |f a (s)| 2 (1-exp(-2B a ∙s 2 ))I ds = I beam t r e 2 V xtal V ASU P A Σ a R. W. James (1947)
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Compton scattering I compton - scattered photons/steradian I beam - incident (photons/s/m 2 ) t- exposure time (s) r e - classical electron radius (2.818x10 -15 m) V xtal - volume of crystal (in m 3 ) V ASU - asymmetric unit (in m 3 ) P- polarization factor A- absorption factor a- particular atom in the ASU θ- Bragg angle κ- photon energy (keV) / 511 keV Z a - atomic number f a (s)- atomic structure amplitude (electrons) s- scattering length (sin(θ)/λ) Z a - |f a (s)|I compton = I beam t r e 2 Σ a V xtal P A V ASU 1+κ (1-cos(θ)) 2 R. W. James (1947)
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Exposure time exposure time (s) CC to correct model
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Crystal Size crystal size (um) CC to correct model
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Shutter Jitter rms timing error (% exposure) CC to correct model
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Site Decay Gd site half-dose (MGy) CC to correct model
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Detective Quantum Efficiency fraction of photons “detected” CC to correct model
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read-out noise read-out nosie (“extra” photons) CC to correct model Q315r Q315 Mar 325HE Pilatus
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