A relatively large discrepancy was found in the molar volume of silicon crystals used to determine the Avogadro constant by means of the X-ray and crystal density (XRCD) method. Voids are suspected to cause the difference in the molar volume. Infrared laser scattering tomography, Secco-etching, electron spin resonance, and X-ray topography have been applied to the silicon crystal of the National Research Laboratory of Metrology to detect voids. However, no voids were observed in the crystal.
['Kan Nakayama', 'Hiroyuki Fujimoto', 'Tetsuya Ishikawa', 'Hiroshi Takeno']
Silicon molar volume discrepancy: studies of the NRLM crystal