Example - 123-high Tc superconductors(\\erice_server – YBCO texture\ybco.zip)• CuKa Bragg-Brentano diffractometer (Siemens)• sample back packed in holder• high quality data collection - used in original publication by (Phys. Rev. B37, 7960-7962, 1988)• presumably platy habit crystals - texture or “preferred orientation” about 001• Question – how to refine the texture (preferred orientation?• Do Rietveld refinement with different texture models

March-DollaseSpherical Harmonics - cylindrical sample symmetry

• No texture model• Poor fit - Rwp = 10.4%• Especially some peaks!

• Harmonic Model L=6• Much better fit - Rwp = 8.3%• Not a lot different from MD and L=4 fits

0.075

0.08

0.085

0.09

0.095

0.1

0.105

no PO H L=2 H L=4 H L=6 H L=8 MD

Residuals for Various Texture Models

Rw

p

Refinement of YBa2Cu3O7-d X-Ray Powder Data with Texture

• Great improvement of the fit • March-Dollase better than L=2 Harmonic model• L=6 Harmonic model about optimum

no. parms 20 22 25 29 34 21

POLFPLOT - Radial Distribution for Harmonic Model L=6

Hkl = 001

Normal In plane

Cut through pole figure – axial distribution

Pole figure – projection down z-sample axis

001 pole distribution

100 pole distribution

Makes sense! Crystals are plates with 001 normalsperpendicular to BB sample surface