Influence of carbon-ion irradiation on the superconducting critical properties of MgB2 thin films (vol 32, 025006, 2019)

Abstract

We have found that there was an error in the calculation of the atomic density of Mg and B in MgB2. The number of MgB2 molecules per cm3 (pMgB2) is around 3.4×1022, so the number of Mg and B atoms per cm3 must be equal to pMgB2 and twice that of pMgB2, respectively. However, the number of Mg and B atoms per cm3 presented in page 7 correspond to 1/3 and 2/3 of pMgB2, respectively. In order to estimate the atomic density, the mass density of bulk value is much more useful than that of strained sample such as a thin film. Since MgB2 has the mass density of 2.57 g cm-3 and the molar mass of 45.93 g mol-1, and Avogadro's number NA ？ 6.02 × 1023 mol-1, the pMgB2 is approximately 3.37 × 1022 molecules cm-3. Therefore, the number of Mg and B atoms per cm3 in MgB2 must be ∼3.37 × 1022 atoms cm-3 and 6.74 × 1022 atoms cm-3, respectively, and the atomic density of MgB2 is around 10.11 × 1022 atoms cm-3. We believe that the change in atomic density does not lead to any significant issues for all the results and conclusions drawn in the paper. ？ 2021 Institute of Physics Publishing. All rights reserved.