Molecular Dynamics Algorithms

The DL_POLY_2 MD algorithms are all couched in the form of the Verlet Leapfrog integration algorithm [12]. NVE, NVT, NPT and N $\underline{\underline{\bf\sigma}}$T ensembles are available, with a selection of thermostats and barostats. A parallel version of the SHAKE algorithm [13] called RD-SHAKE is used for bond constraints [11]. Fincham's implicit quaternion algorithm (FIQA) [14] is available for rigid molecular species. Rigid molecular species linked by rigid bonds are handled with an algorithm of our own devising, called the QSHAKE algorithm [15].

The following MD algorithms are available:

1. Verlet leapfrog;
2. Verlet leapfrog with RD-SHAKE;
3. Rigid molecules with FIQA and RD-SHAKE;
4. Linked rigid molecules with QSHAKE [15];
5. Berendsen constant T algorithm with Verlet or RD-SHAKE [16];
6. Evans constant T algorithm with Verlet or RD-SHAKE [17];
7. Hoover constant T algorithm with Verlet or RD-SHAKE [18];
8. Berendsen constant T algorithm with FIQA and RD-SHAKE [16];
9. Berendsen constant T algorithm with QSHAKE [16];
10. Hoover constant T algorithm with FIQA and RD-SHAKE [18];
11. Hoover constant T algorithm with QSHAKE [18];
12. Berendsen constant T,P algorithm with RD-SHAKE [16];
13. Berendsen constant T, $\underline{\underline{\bf\sigma}}$ algorithm with RD-SHAKE [16];
14. Hoover constant T,P algorithm with RD-SHAKE [18];
15. Hoover constant T, $\underline{\underline{\bf\sigma}}$ algorithm with RD-SHAKE [18];
16. Berendsen constant T,P algorithm with FIQA and RD-SHAKE [16];
17. Berendsen constant T,P algorithm with QSHAKE [16];
18. Berendsen constant T, $\underline{\underline{\bf\sigma}}$ algorithm with FIQA and RD-SHAKE [16];
19. Berendsen constant T, $\underline{\underline{\bf\sigma}}$ algorithm with QSHAKE [16];
20. Hoover constant T,P algorithm with FIQA and RD-SHAKE [18];
21. Hoover constant T,P algorithm with QSHAKE [18];
22. Hoover constant T, $\underline{\underline{\bf\sigma}}$ algorithm with FIQA and RD-SHAKE [18];
23. Hoover constant T, $\underline{\underline{\bf\sigma}}$ algorithm with QSHAKE [18];

A variant of DL_POLY_2 that handles the time reversible, multiple timestep RESPA algorithm [19,20] is also available for atomic systems and rigid ion systems [21], but it is not applicable to systems which have rigid body molecules or constraints.