Simulations: Difference between revisions

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===Special Usage Notes===
===Special Usage Notes===
By default, LAMMPS normalizes the temperature by an amount (dof - d), where dof is the system's total number of degrees of freedom and d is the dimensionality of the simulation. (dof - d) is used to account for the center-of-mass motion of the system. This is correct except when there is a proper frame of reference for the system, e.g., in a Langevin dynamics simulation in which the implicit background solvent has zero average velocity. In this case it is necessary to use the command [http://lammps.sandia.gov/doc/compute_modify.html compute_modify] to ensure dof is used instead of (dof - d), as follows.
By default, LAMMPS normalizes the temperature by an amount (dof - d), where dof is the system's total number of degrees of freedom and d is the dimensionality of the simulation. Subtracting d accounts for the center-of-mass motion of the system. This is correct except when there is a proper frame of reference for the system, e.g., in a Langevin dynamics simulation in which the implicit background solvent has zero average velocity. In this case it is necessary to use the command [http://lammps.sandia.gov/doc/compute_modify.html compute_modify] to ensure dof is used instead of (dof - d). An example is as follows.

<pre>
compute myTemp all temp
compute_modify myTemp extra 0
thermo_modify temp myTemp
</pre>


== Monte Carlo simulations ==
== Monte Carlo simulations ==

Revision as of 18:51, 7 June 2014

Introduction

Assorted topics relevant to programming particle-based simulation codes and to using these codes for the modeling of a wide range of systems, notably complex fluids.

Molecular dynamics simulations

Special Usage Notes

By default, LAMMPS normalizes the temperature by an amount (dof - d), where dof is the system's total number of degrees of freedom and d is the dimensionality of the simulation. Subtracting d accounts for the center-of-mass motion of the system. This is correct except when there is a proper frame of reference for the system, e.g., in a Langevin dynamics simulation in which the implicit background solvent has zero average velocity. In this case it is necessary to use the command compute_modify to ensure dof is used instead of (dof - d). An example is as follows.

compute myTemp all temp
compute_modify myTemp extra 0
thermo_modify temp myTemp

Monte Carlo simulations