The paper by Berendsen, Postma, van Gunsteren, Di Nola, and Haak (1984) introduces a method for molecular dynamics (MD) simulations that couples a system to an external bath to maintain constant temperature or pressure. This method allows for adjustable time constants in the coupling, making it applicable to various variables and gradients. The approach uses a leap-frog algorithm for general cases involving constraints with coupling to both a constant temperature and pressure bath. The method is extended to include internal constraints and is tested on liquid water simulations using the SPC model. The results show that the method effectively controls temperature and pressure, with minimal impact on static properties. However, fluctuations in global properties are strongly influenced by the coupling time constants, especially for values less than 0.1 ps. The method is found to be numerically stable and suitable for nonequilibrium molecular dynamics (NEMD) simulations, allowing for the incorporation of gradients in temperature, pressure, and velocities. The method has been successfully applied to various simulations, including polypeptide and protein studies, and is now part of the GROMOS program library. The paper concludes that the method is reliable and practical for simulating physical systems under controlled conditions.The paper by Berendsen, Postma, van Gunsteren, Di Nola, and Haak (1984) introduces a method for molecular dynamics (MD) simulations that couples a system to an external bath to maintain constant temperature or pressure. This method allows for adjustable time constants in the coupling, making it applicable to various variables and gradients. The approach uses a leap-frog algorithm for general cases involving constraints with coupling to both a constant temperature and pressure bath. The method is extended to include internal constraints and is tested on liquid water simulations using the SPC model. The results show that the method effectively controls temperature and pressure, with minimal impact on static properties. However, fluctuations in global properties are strongly influenced by the coupling time constants, especially for values less than 0.1 ps. The method is found to be numerically stable and suitable for nonequilibrium molecular dynamics (NEMD) simulations, allowing for the incorporation of gradients in temperature, pressure, and velocities. The method has been successfully applied to various simulations, including polypeptide and protein studies, and is now part of the GROMOS program library. The paper concludes that the method is reliable and practical for simulating physical systems under controlled conditions.