Following problems with peak shape we recorded in cycle 98-3 several diagrams of a silicium standard (8 mm sample diameter) at 1.3 Å with different incident divergences alpha1 and different horizontal monochromator apertures (SlitM_L/R). We give here the results of Rietveld refinements with FullProf.
Numor | alpha1 (min) | slitM_L (mm) | slitM_R (mm) | acq time (s) | zero shift (deg) | wavelength (Angstroem) | scale | U | V | W | eta | ass1 | ass2 | Rp (%) | RBragg (%) |
69374 | 27 | 30 | 30 | 30 | -0.156(8) | 1.3013(2) | 11.4(2) | 7.5(2) | -4.5(2) | 0.90(3) | 0.05(3) | 0.18(2) | 0.054(7) | 15.8 | 8.76 |
69375 | 27 | 0 | 30 | 30 | +0.092(7) | 1.2921(2) | 5.81(9) | 3.6(1) | -2.1(1) | 0.52(3) | 0.10(3) | 0.22(2) | 0.072(8) | 19.8 | 10.7 |
69376 | 27 | 30 | 0 | 30 | -0.369(5) | 1.3096(1) | 5.49(7) | 2.94(9) | -1.62(8) | 0.43(2) | 0.09(2) | 0.21(1) | 0.053(6) | 15.5 | 6.84 |
69379 | 20 | 30 | 30 | 30 | -0.075(7) | 1.2957(2) | 5.00(7) | 5.8(2) | -4.1(1) | 0.90(3) | 0.10(2) | 0.20(1) | 0.059(7) | 16.5 | 7.96 |
69378 | 20 | 0 | 30 | 30 | +0.123(6) | 1.2893(1) | 3.04(4) | 2.47(9) | -1.70(9) | 0.47(2) | 0.18(3) | 0.22(1) | 0.066(7) | 18.6 | 9.18 |
69377 | 20 | 30 | 0 | 30 | -0.349(4) | 1.30495(9) | 1.94(2) | 1.92(6) | -1.40(6) | 0.41(2) | 0.14(2) | 0.20(1) | 0.05(6) | 17.0 | 6.44 |
69380 | 10 | 30 | 30 | 30 | +0.049(6) | 1.2906(1) | 1.27(2) | 3.3(1) | -2.6(1) | 0.66(2) | 0.18(2) | 0.24(1) | 0.075(7) | 20.8 | 7.46 |
69382 | 10 | 0 | 30 | 60 | +0.146(5) | 1.2876(1) | 1.91(3) | 1.94(7) | -1.57(7) | 0.45(2) | 0.18(3) | 0.27(2) | 0.073(7) | 20.1 | 8.21 |
69383 | 10 | 0 | 15 | 60 | +0.023(4) | 1.29127(7) | 1.05(2) | 0.91(4) | -0.74(5) | 0.29(1) | 0.23(2) | 0.24(1) | 0.07(7) | 20.8 | 7.31 |
69381 | 10 | 30 | 0 | 60 | -0.244(5) | 1.29967(8) | 0.64(1) | 0.97(4) | -0.83(5) | 0.29(1) | 0.27(3) | 0.22(1) | 0.059(7) | 24.7 | 7.52 |
69384 | 10 | 15 | 0 | 60 | -0.210(4) | 1.29859(7) | 0.571(9) | 0.66(3) | -0.60(4) | 0.25(1) | 0.28(2) | 0.23(1) | 0.063(7) | 22.5 | 6.25 |
As a conclusion you should not use the alpha1=10' Soller collimator in combination with the left half of the copper monochromator but with the right one. Anyway you should not use the whole monochromator as its two columns of copper crystals give an intensity hole in the center of the beam and therefore a bad peak shape. Normally its better to use the left half of the monochromator as this gives a better resolution (and higher wavelength) due to the higher take-off angle. Only for the 10' Soller collimator you should better use the other half until the collimator will have been repaired.
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