TY - JOUR
T1 - Kinematic and dynamical CBED for solving thin organic films at low temperature; experimental tests with anthracene
AU - Wu, J. S.
AU - Spence, John
PY - 2002/11/1
Y1 - 2002/11/1
N2 - Low-dose, low-temperature kinematic and dynamical convergent-beam electron diffraction (CBED) patterns from thin organic crystalline films have been used for the measurement of structure-factor amplitudes and phases. Kinematic conditions are identified by the observation of uniform intensity within the CBED discs and used to determine structure-factor magnitudes. CBED patterns from thicker regions affected by multiple scattering give structure-factor signs, which are varied for best fit. The use of a small probe (and the Kohler SAD mode) minimizes bending artifacts. A new method of thickness determination is evaluated. The approach is tested using experimental data from the centrosymmetric anthracene structure, the results compared with direct methods, and a potential map derived from experimental data. The faint peaks due to H-atom positions may be distinguished. Key issues influencing the validity of the method such as the appropriate dimension of the structure-factor matrix, sample thickness and crystal orientation are discussed.
AB - Low-dose, low-temperature kinematic and dynamical convergent-beam electron diffraction (CBED) patterns from thin organic crystalline films have been used for the measurement of structure-factor amplitudes and phases. Kinematic conditions are identified by the observation of uniform intensity within the CBED discs and used to determine structure-factor magnitudes. CBED patterns from thicker regions affected by multiple scattering give structure-factor signs, which are varied for best fit. The use of a small probe (and the Kohler SAD mode) minimizes bending artifacts. A new method of thickness determination is evaluated. The approach is tested using experimental data from the centrosymmetric anthracene structure, the results compared with direct methods, and a potential map derived from experimental data. The faint peaks due to H-atom positions may be distinguished. Key issues influencing the validity of the method such as the appropriate dimension of the structure-factor matrix, sample thickness and crystal orientation are discussed.
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U2 - 10.1107/S0108767302015830
DO - 10.1107/S0108767302015830
M3 - Article
C2 - 12388877
AN - SCOPUS:0036854228
SN - 0108-7673
VL - 58
SP - 580
EP - 589
JO - Acta Crystallographica Section A: Foundations of Crystallography
JF - Acta Crystallographica Section A: Foundations of Crystallography
IS - 6
ER -