## LAMMPS Deficiencies

Return to top-level of LAMMPS documentation.

This is a brief list of features lacking in the current version of LAMMPS. Some of these deficiencies are because of lack of time/interest; others are just hard!

- The calculation of pressure does not include a long-range Van der Waals correction. This would be a constant for constant volume simulations but is a source of error for constant pressure simulations where the box-size varies dynamically.
- The smoothed Coulomb style cannot be used with class 2 force fields.
- The minimizer does not work with constant pressure conditions, nor for some kinds of fixes (constraints).
- No support for non-rectilinear boxes (e.g. Parinello-Rahman pressure control).
- SHAKE fixes cannot be combined with rREPSA.
- In the current F90 version of LAMMPS, Ewald computations are 2x slower on some machines than they were in the earlier F77 version. This is probably because of F90 compiler treatment of allocatable arrays. This slowdown is not an issue with PPPM, which is more commonly used anyway.
- LAMMPS uses a spatial-decomposition of the simulation domain, but no other load-balancing -- thus some geometries or density fluctuations can lead to load imbalance on a parallel machine.