NPT MD simulations allow to have fixed pressure, while the cell shape changes. At the moment only isotropic volume change is possible: the cell is scaled by a scalar factor, the angles stay the same and the ratio of length too. In order to observe phase transition, it's important that the cell can change shape (example: titanium hcp -> bcc transition around 1150K).
NPT Nosé Hoover comes from Martyna, G. J., Tuckerman, M. E., Tobias, D. J., & Klein, M. L. (1996). Explicit reversible integrators for extended systems dynamics. Molecular Physics, 87(5), 1117-1157. This paper completely describes the exact time discretization that needs to be implemented.
It's possible to implement a full anisotropic method (angles and length). It should be possible to only modify the current implementation (NPTNoseHooverState and init/step functions) in order to accept all possibilities (x, y, z lengths variations and angles) with a total of 6 degrees of freedom.
NPT MD simulations allow to have fixed pressure, while the cell shape changes. At the moment only isotropic volume change is possible: the cell is scaled by a scalar factor, the angles stay the same and the ratio of length too. In order to observe phase transition, it's important that the cell can change shape (example: titanium hcp -> bcc transition around 1150K).
NPT Nosé Hoover comes from Martyna, G. J., Tuckerman, M. E., Tobias, D. J., & Klein, M. L. (1996). Explicit reversible integrators for extended systems dynamics. Molecular Physics, 87(5), 1117-1157. This paper completely describes the exact time discretization that needs to be implemented.
It's possible to implement a full anisotropic method (angles and length). It should be possible to only modify the current implementation (NPTNoseHooverState and init/step functions) in order to accept all possibilities (x, y, z lengths variations and angles) with a total of 6 degrees of freedom.