The following tutorial pertains to NVT Monte simulation of a Lennard-Jones system.

Linking to the simulation builder library/header

First of all, the Simulation Builder header file should be included:

#include <glotzilla++.h>

This tells the compiler about all of the pre-defined Glotzilla classes. We will now be able to access the McSimulation class within the Simulation Builder library and can create an instance of it:

#include <glotzilla++.h>

int main(int argc, char ** argv) 
{       
   McSimulation my_simulation;
   return 0;
}

Setting up the simulation

Having declared an instance of McSimulation my_simulation, we can now set up the MC simulation. An MC code needs a few aspects of it to be defined in order to work:

• particles - objects that exist in the simulation.
• interaction - specifies how particles interact with each other.
• trial moves - the type of trial moves performed on the particles/system.
• potential routine - calculates the potential energy of the system.
• boundary conditions - the space accessible to the particles.
• random number generator - generates random numbers for performing trial moves.

In the following code, we will:

• add two particles at <0, 0, 0> and <1, 1, 1>
• set the interaction between particles as Lennard-Jones.
• add translation as a trial move.
• set the code to use a brute potential routine.
• set the boundary of the box to be periodic where Lx = Ly = Lz = 5
• set the standard StdLibErand?48 as the random number generator

#include "glotzilla++.h"

int main(int argc, char ** argv) 
{       
   McSimulation my_simulation;

   my_simulation.AddParticle(new McPointParticle(0,0,0));
   my_simulation.AddParticle(new McPointParticle(1,1,1));
   my_simulation.SetInteraction(new LennardJones);
   my_simulation.AddTrialMove (new TrialTranslation);
   my_simulation.SetPotentialRoutine(new BrutePotential);
   my_simulation.SetBoundaryConditions(new PeriodicBoundary(5));
   my_simulation.SetRandomNumberGenerator(new StdLibErand48);

   return 0;
}

Performing the trial moves

To advance the simulation through simulation i.e. perform the actual MC trial moves, we need only use the "++" operator defined in McSimulation. he following excerpt of code will advance the simulation through 20000 MC cycles and then exit.

#include "glotzilla++.h"

int main(int argc, char ** argv) 
{       
   McSimulation my_simulation;

   my_simulation.AddParticle(new McPointParticle(0,0,0));
   my_simulation.AddParticle(new McPointParticle(1,1,1));
   my_simulation.SetInteraction(new LennardJones);
   my_simulation.AddTrialMove (new TrialTranslation);
   my_simulation.SetPotentialRoutine(new BrutePotential);
   my_simulation.SetBoundaryConditions(new PeriodicBoundary(5));
   my_simulation.SetRandomNumberGenerator(new StdLibErand48);

   for (int i=0; i<20000; i++)
       my_simulation++;

   return 0;
}

Getting information from the simulation

Compiling the code

To compile the code you will need to use the "glotzcc" command. The glotzcc command calls the mpic++ compiler and gives it the appropriate library and header search paths. Within your shell, execute the following command:

glotzcc MCMinimalSimulation.cpp

where MCMinimalSimulation.cpp is the name of the file where the code resides.

Problems

Refer to the FAQ? page.