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Overview of Drude induced dipoles

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Tutorial for Thermalized Drude oscillators in LAMMPS

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This tutorial explains how to use Drude oscillators in LAMMPS to +simulate polarizable systems using the USER-DRUDE package. As an +illustration, the input files for a simulation of 250 phenol molecules +are documented. First of all, LAMMPS has to be compiled with the +USER-DRUDE package activated. Then, the data file and input scripts +have to be modified to include the Drude dipoles and how to handle +them.

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Overview of Drude induced dipoles

Polarizable atoms acquire an induced electric dipole moment under the action of an external electric field, for example the electric field created by the surrounding particles. Drude oscillators represent @@ -148,12 +158,12 @@ particle remains close ot the core. The values of Drude mass, Drude charge, and force constant can be chosen following different strategies, as in the following examples of polarizable force fields:

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    • Lamoureux and Roux suggest adopting a global half-stiffness, \(K_D\) = 500 kcal/(mol Ang \({}^2\)) - which corresponds to a force constant \(k_D\) = 4184 kJ/(mol Ang \({}^2\)) - for all types of core-Drude bond, a global mass \(m_D\) = 0.4 g/mol (or u) for all types of Drude particles, and to calculate the Drude charges for individual atom types from the atom polarizabilities using equation (1). This choice is followed in the polarizable CHARMM force field.
    • Alternately Schroeder and Steinhauser suggest adopting a global charge \(q_D\) = -1.0e and a global mass \(m_D\) = 0.1 g/mol (or u) for all Drude particles, and to calculate the force constant for each type of core-Drude bond from equation (1). The timesteps used by these authors are between 0.5 and 2 fs, with the degrees of freedom of the Drude oscillators kept cold at 1 K.
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#. In both these force fields hydrogen atoms are treated as non-polarizable. -The motion of of the Drude particles can be calculated by minimizing +