Gravity and anisotropy effects in the volume determination of Si spheres for the kilogram realisation

摘要

The counting of(28)Si atoms plays a fundamental role in the realisation of the unit of mass in terms of stipulated values of fundamental physical constants. In this realisation, the measurement of the volume of a(28)Si sphere is a fundamental step. This paper reports a finite element analysis of the self-weight effect on the volume determination, taking the crystal anisotropy into account. The sphere volume might be overestimated from 0.3 x 10(-9)to 5.1 x 10(-9)(relative terms), depending on the crystal orientation and measurement procedure.