  The bulk moduli of PbS$_{x}$Se$_{1-x}$, PbS$_{x}$Te$_{1-x}$, and
PbSe$_{x}$Te$_{1-x}$ have been recently determined [E. Skordas, Materials
Science in Semiconductor Processing 43 (2016) 65-68] by employing a
thermodynamical model, the so called $cB\Omega$ model, which has been found to
give successful results in several applications of defects in solids. Here, we
suggest an alternative procedure for this determination which combines the
$cB\Omega$ model with the modified Born theory. The results are in satisfactory
agreement with those deduced independently by the generalized gradient
approximation approach.
