# DL POLY

DL_POLY [1] [2] is a general purpose serial and parallel molecular dynamics simulation package developed at Daresbury Laboratory by W. Smith, T.R. Forester and I.T. Todorov

## Units

DL_POLY employs an interesting set of units which have molecular relevance [3].:

 physical quantity symbol unit value time ${\displaystyle t_{0}}$ ${\displaystyle 1\times 10^{-12}}$ seconds (picoseconds) length ${\displaystyle l_{0}}$ ${\displaystyle 1\times 10^{-10}}$ metres (Angstroms) mass ${\displaystyle m_{0}}$ ${\displaystyle 1.66054\times 10^{-27}}$ kilograms (amu) charge ${\displaystyle q_{0}}$ ${\displaystyle 1.60218\times 10^{-19}}$ Coulombs (electron charge) energy ${\displaystyle E_{0}=m_{0}(l_{0}/t_{0})^{2}}$ ${\displaystyle 1.66054\times 10^{-23}}$ Joules = 10 J mol${\displaystyle ^{-1}}$ pressure ${\displaystyle p_{0}=E_{0}/l_{0}^{3}}$ ${\displaystyle 1.66054\times 10^{7}}$ Pascal = 166.054 bar Planck constant ${\displaystyle \hbar }$ ${\displaystyle 6.35078E_{0}t_{0}}$ Boltzmann constant ${\displaystyle k_{B}}$ ${\displaystyle 0.83145E_{0}/K}$

## Force field

The force field used in DL_POLY consists (or can consist) of the following components [4]:

• Chemical bond potentials:
• Angle potentials:
• Dihedral angle potentials:
• Inversion angle potentials:
• Tethering potentials:
• Non-bonded potentials
• Three-body potentials
• Four-body potentials
• Metal potentials
• External fields

## Constraint algorithms

DL POLY can use either the SHAKE or the RATTLE algorithms as well as Q-SHAKE [5].

## Versions of DL_POLY

The current version of DL_POLY is DL_POLY_4.07

#### Previous versions

DL_POLY_2

DL_POLY_2 was designed for simulations of up to 30,000 atoms and on parallel computers using up to 100 processors.

DL_POLY_3

DL_POLY_3 was designed for simulations of order 100,000 to 1,000,000 atoms running on up to 1000 processors.

• DL_POLY_3 does not handle rigid body molecules.

#### Other versions

DL_MULTI

A DL_POLY package to simulate rigid molecules with multipoles [6].

## Visualising DL_POLY output

The visualisation program VMD is capable of displaying the HISTORY trajectory file.