AbstractUsing a total of 1052 Bragg reflections of silicon, an X‐ray investigation has been carried out to deduce the anharmonic thermal parameter β, apart from the estimation of the harmonic contribution of the thermal vibration at room temperature. Reflections of typeh+k+l= 4n, and 4n± 1 were used to estimate these parameters using MoK α radiation and a Nonius CAD‐4 X‐ray diffractometer. We obtainBsi, = 0.451(0.008) Å2and βsi= 0.279(2.630) eV Å−3withR= 3.12%. The presentBand β values are in very good agreement with the e