On the isothermal-isobaric ensemble partition function

We briefly review the isothermal-isobaric ensemble partition function corre ctly derived by Corti and Soto-Campos [J. Chem. Phys. 108, 7959 (1998)] fro m the view point of usual simulations in which the external bath of a syste m is appropriately approximated. We show that, for the homogeneous system, the partition function can be reduced to the result of Attard [J. Chem. Phy s. 103, 9884 (1995)] which was criticized by Corti and Soto-Campos. We conc lude that the volume scale cannot be defined in general but in some particu lar cases and the recently controverted volume scales are those of the case s. We also confirm the validity of Brown's [Mol. Phys. 1, 68 (1958)] partit ion function which has never been used in simulations before, by demonstrat ing that it is equivalent to the one of Corti and Soto-Campos. (C) 2001 Ame rican Institute of Physics.