Remarks on ‘‘Constant-temperature molecular dynamics with momentum conservation’’

In a recent paper K. Cho, J. D. Joannopoulos, and L. Kleinmann, Phys. Rev. E 47, 3145 (1993), the Nos\'e-Hoover canonical dynamics method was shown to generate the canonical ensemble in systems with no external forces only for the special case of zero total linear momentum. Here, it is demonstrated that this is not a general failing of Nos\'e-Hoover--type methods but a specific feature of the simple Nos\'e-Hoover scheme. The slightly more complex Nos\'e-Hoover chain method which includes a linear chain of coupled variables to control the temperature rather than a single variable is sufficient to yield the canonical ensemble for the case of nonzero linear momentum.