Combined structure-factor phase measurement and theoretical calculations for mapping of chemical bonds in GaN.
For non-centrosymmetric crystals, the refinement of charge-density maps requires highly accurate measurements of structure-factor phase, which can now be obtained using the extinction-free convergent-beam electron microdiffraction method. We report here accurate low-order structure-factor phases and amplitudes for gallium nitride (GaN) in the wurtzite structure. The measurement accuracy is up to 0.1% for amplitude and 0.2 degrees for phases. By combining these with high-order structure factors from electronic structure calculation, charge-density maps were obtained. Fine bonding features suggest that the Ga-N bonds are polar and covalent, with charge transfer from Ga to N; however, the polarity effect is extremely small.
Jiang
B
B
Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
Zuo
J M
JM
Holec
D
D
Humphreys
C J
CJ
Spackman
M
M
Spence
J C H
JC