@@ -5,10 +5,11 @@ To run a simulation using LAMMPS, you need to write an input script
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containing a series of commands for LAMMPS to execute, similar to Python
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or Bash scripts. For clarity, the input scripts for this tutorial will
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be divided into five categories, which will be filled out step by step.
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- To set up this tutorial, navigate to the directory
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- where you want to store your files. Create a folder if needed and
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- place the initial input file, **initial.lmp **, into it. Then, open the
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- file in a text editor of your choice, and copy the following into it:
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+ To set up this tutorial using LAMMPS graphical user interface
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+ (LAMMPS--GUI) :cite: `lammps_gui_docs `, select ``Start LAMMPS Tutorial 1 ``
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+ from the ``Tutorials `` menu and follow the instructions. This will
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+ select (or create, if needed) a folder, place the initial input
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+ file **initial.lmp ** in it, and open the file in the LAMMPS--GUI Editor window:
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.. code-block :: lammps
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@@ -17,18 +18,15 @@ file in a text editor of your choice, and copy the following into it:
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# 2) System definition
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# 3) Settings
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# 4) Visualization
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- # 5) Run
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+ # 5) Run
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- .. admonition :: Optional: follow this tutorial using LAMMPS-GUI
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+ .. admonition :: If you are not using LAMMPS-GUI
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:class: gui
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- This tutorial can also be followed using LAMMPS graphical
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- user interface (LAMMPS--GUI) :cite: `lammps_gui_docs `.
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- Select ``Start LAMMPS Tutorial 1 `` from
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- the ``Tutorials `` menu of LAMMPS--GUI, and follow the
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- instructions. This will select (or create, if needed) a folder, place
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- the initial input file **initial.lmp ** in it, and open the file in
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- the LAMMPS--GUI Editor window.
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+ All tutorials can be followed without using LAMMPS-GUI. To
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+ do so, create a new folder and add a file named **initial.lmp **
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+ inside it. Open the file in a text editor of your choice and
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+ copy the previous lines into it.
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Everything that appears after a hash symbol (#) is a comment
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and ignored by LAMMPS. These five categories are not required in every input script an do not
@@ -96,15 +94,11 @@ slab geometries.
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Each LAMMPS command is accompanied by extensive online documentation
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that details the different options for that command :cite: `lammps_docs `.
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-
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- .. admonition :: If you are using LAMMPS-GUI
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- :class: gui
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-
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- From the LAMMPS--GUI editor buffer, you can access the documentation by
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- right-clicking on a line containing a command (e.g., ``units lj ``)
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- and selecting ``View Documentation for `units' ``. This action
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- should prompt your web browser to open the corresponding URL for the
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- online manual.
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+ From the LAMMPS--GUI editor buffer, you can access the documentation by
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+ right-clicking on a line containing a command (e.g., ``units lj ``)
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+ and selecting ``View Documentation for `units' ``. This action
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+ should prompt your web browser to open the corresponding URL for the
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+ online manual.
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The next step is to create the simulation box and populate it with
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atoms. Modify the ``System definition `` category of
@@ -220,24 +214,21 @@ You can now run LAMMPS (basic commands for running LAMMPS
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are provided in Ref. :cite: `lammps_run_basics `).
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The simulation should finish quickly.
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- .. admonition :: If you are using LAMMPS-GUI
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- :class: gui
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-
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- With the default settings, LAMMPS--GUI will open two windows: one
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- displaying the console output and another with a chart. The ``Output `` window
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- will display information from the executed commands, including the
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- total energy and pressure at step 0,
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- as specified by the thermodynamic data request. Since no actual simulation
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- steps were performed, the ``Charts `` window will be empty.
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-
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- **Snapshot image -- ** At this point, you can create a snapshot image of the current system
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- using the ``Image Viewer `` window, which can be accessed by
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- clicking the ``Create Image `` button in the ``Run `` menu. The
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- image viewer works by instructing LAMMPS to render an image of the
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- current system using its internal rendering library via the ``dump image ``
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- command. The resulting image is then displayed, with various
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- buttons available to adjust the view and rendering style. This will always
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- capture the current state of the system.
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+ With the default settings, LAMMPS--GUI will open two windows: one
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+ displaying the console output and another with a chart. The ``Output `` window
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+ will display information from the executed commands, including the
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+ total energy and pressure at step 0,
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+ as specified by the thermodynamic data request. Since no actual simulation
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+ steps were performed, the ``Charts `` window will be empty.
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+
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+ **Snapshot image -- ** At this point, you can create a snapshot image of the current system
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+ using the ``Image Viewer `` window, which can be accessed by
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+ clicking the ``Create Image `` button in the ``Run `` menu. The
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+ image viewer works by instructing LAMMPS to render an image of the
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+ current system using its internal rendering library via the ``dump image ``
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+ command. The resulting image is then displayed, with various
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+ buttons available to adjust the view and rendering style. This will always
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+ capture the current state of the system.
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Energy minimization
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-------------------
@@ -259,17 +250,14 @@ as the minimizer algorithm cannot find a way to lower the potential
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energy. Note that, except for trivial systems, minimization algorithms will find a
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local minimum rather than the global minimum.
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- .. admonition :: If you are using LAMMPS-GUI
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- :class: gui
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-
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- Run the minimization and observe that LAMMPS-GUI captures the output
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- and updates the chart in real time. This run executes quickly (depending
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- on your computer's capabilities), but LAMMPS-GUI may fail to capture some
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- of the thermodynamic data. In that
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- case, use the ``Preferences `` dialog to reduce the data update
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- interval and switch to single-threaded, unaccelerated execution in the
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- ``Accelerators `` tab. You can repeat the run; each new attempt will start
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- fresh, resetting the system and re-executing the script from the beginning.
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+ Run the minimization and observe that LAMMPS-GUI captures the output
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+ and updates the chart in real time. This run executes quickly (depending
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+ on your computer's capabilities), but LAMMPS-GUI may fail to capture some
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+ of the thermodynamic data. In that
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+ case, use the ``Preferences `` dialog to reduce the data update
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+ interval and switch to single-threaded, unaccelerated execution in the
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+ ``Accelerators `` tab. You can repeat the run; each new attempt will start
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+ fresh, resetting the system and re-executing the script from the beginning.
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Run the minimization. The potential energy, :math: `U`, decreases
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from a positive value to a negative value
@@ -286,11 +274,10 @@ decreases - first rapidly - then more gradually, before plateauing at a
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negative value. This indicates that the atoms have moved to reasonable
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distances from one another.
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- ..
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- Create and save a snapshot image of the simulation state after the
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- minimization, and compare it to the initial image. You should observe
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- that the atoms are *clumping together* as they move toward positions
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- of lower potential energy.
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+ Create and save a snapshot image of the simulation state after the
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+ minimization, and compare it to the initial image. You should observe
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+ that the atoms are *clumping together * as they move toward positions
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+ of lower potential energy.
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Molecular dynamics
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------------------
@@ -394,20 +381,17 @@ it reaches a plateau value of about -0.25. The kinetic energy,
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increases rapidly during molecular dynamics until it reaches
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a plateau value of about 1.5.
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- .. admonition :: If you are using LAMMPS-GUI
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- :class: gui
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-
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- From the information
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- printed in the ``Output `` window, one can see that the temperature
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- starts from 0 but rapidly reaches the requested value and
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- stabilizes itself near :math: `T=1 ` temperature units. One can also observe that
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- the potential energy, :math: `U`, rapidly decreases during energy
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- minimization (see the figure below). After
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- the molecular dynamics simulation starts, :math: `U` increases until
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- it reaches a plateau value of about -0.25. The kinetic energy,
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- :math: `K`, is equal to zero during energy minimization and then
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- increases rapidly during molecular dynamics until it reaches
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- a plateau value of about 1.5.
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+ From the information
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+ printed in the ``Output `` window, one can see that the temperature
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+ starts from 0 but rapidly reaches the requested value and
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+ stabilizes itself near :math: `T=1 ` temperature units. One can also observe that
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+ the potential energy, :math: `U`, rapidly decreases during energy
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+ minimization (see the figure below). After
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+ the molecular dynamics simulation starts, :math: `U` increases until
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+ it reaches a plateau value of about -0.25. The kinetic energy,
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+ :math: `K`, is equal to zero during energy minimization and then
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+ increases rapidly during molecular dynamics until it reaches
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+ a plateau value of about 1.5.
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.. figure :: figures/LJ-energy-dm.png
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:class: only-dark
@@ -444,42 +428,38 @@ Run the **initial.lmp** file using LAMMPS again. A file named **dump.lammpstrj**
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must appear alongside **initial.lmp **. The **.lammpstrj ** file can be opened
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using VMD :cite: `vmd_home, humphrey1996vmd ` or OVITO :cite: `ovito_home, ovito_paper `.
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- .. admonition :: If you are using LAMMPS-GUI
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- :class: gui
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+ Use the ``dump image `` command to create snapshot images during the simulation. We
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+ have already explored the ``Image Viewer `` window. Open it again
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+ and adjust the visualization to your liking using the available buttons.
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+ Now you can copy the commands used to create this visualization to the
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+ clipboard by either using the ``Ctrl-D `` keyboard shortcut or
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+ selecting ``Copy dump image command `` from the ``File `` menu.
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+ This text can be pasted into the ``Visualization `` section
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+ of ``PART B `` of the **initial.lmp ** file. This may look like
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+ the following:
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+
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+ .. code-block :: lammps
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- Use the ``dump image ``
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- command to create snapshot images during the simulation. We
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- have already explored the ``Image Viewer `` window. Open it again
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- and adjust the visualization to your liking using the available buttons.
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- Now you can copy the commands used to create this visualization to the
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- clipboard by either using the ``Ctrl-D `` keyboard shortcut or
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- selecting ``Copy dump image command `` from the ``File `` menu.
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- This text can be pasted into the ``Visualization `` section
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- of ``PART B `` of the **initial.lmp ** file. This may look like
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- the following:
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-
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- .. code-block :: lammps
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-
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- dump viz all image 100 myimage-*.ppm type type size 800 800 zoom 1.452 shiny 0.7 fsaa yes &
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- view 80 10 box yes 0.025 axes no 0.0 0.0 center s 0.483725 0.510373 0.510373
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- dump_modify viz pad 9 boxcolor royalblue backcolor white adiam 1 1.6 adiam 2 4.8
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-
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- This command tells LAMMPS to generate NetPBM format images every 100
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- steps. The two ``type `` keywords are for *color * and
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- *diameter *, respectively. Run the **initial.lmp ** using
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- LAMMPS again, and a new window named ``Slide Show `` will pop up.
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- It will show each image created by the ``dump image `` as it is
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- created. After the simulation is finished (or stopped), the slideshow
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- viewer allows you to animate the trajectory by cycling through the
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- images. The window also allows you to export the animation to a movie
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- (provided the FFMpeg program is installed) and to bulk delete those
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- image files.
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-
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- The rendering of the system can be further adjusted using the many
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- options of the ``dump image `` command. For instance, the value for the
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- ``shiny `` keyword is used to adjust the shininess of the atoms, the
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- ``box `` keyword adds or removes a representation of the box, and
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- the ``view `` and ``zoom `` keywords adjust the camera (and so on).
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+ dump viz all image 100 myimage-*.ppm type type size 800 800 zoom 1.452 shiny 0.7 fsaa yes &
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+ view 80 10 box yes 0.025 axes no 0.0 0.0 center s 0.483725 0.510373 0.510373
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+ dump_modify viz pad 9 boxcolor royalblue backcolor white adiam 1 1.6 adiam 2 4.8
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+
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+ This command tells LAMMPS to generate NetPBM format images every 100
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+ steps. The two ``type `` keywords are for *color * and
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+ *diameter *, respectively. Run the **initial.lmp ** using
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+ LAMMPS again, and a new window named ``Slide Show `` will pop up.
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+ It will show each image created by the ``dump image `` as it is
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+ created. After the simulation is finished (or stopped), the slideshow
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+ viewer allows you to animate the trajectory by cycling through the
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+ images. The window also allows you to export the animation to a movie
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+ (provided the FFMpeg program is installed) and to bulk delete those
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+ image files.
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+
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+ The rendering of the system can be further adjusted using the many
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+ options of the ``dump image `` command. For instance, the value for the
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+ ``shiny `` keyword is used to adjust the shininess of the atoms, the
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+ ``box `` keyword adds or removes a representation of the box, and
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+ the ``view `` and ``zoom `` keywords adjust the camera (and so on).
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Improving the script
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====================
@@ -556,12 +536,9 @@ the ``minimize`` command:
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Run the **improved.min.lmp ** file using LAMMPS--GUI. At the end
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of the simulation, a file called **improved.min.data ** is created.
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- .. admonition :: If you are using LAMMPS-GUI
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- :class: gui
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-
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- You can view the contents of **improved.min.data ** from LAMMPS--GUI, by
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- right-clicking on the file name in the editor and selecting the entry
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- ``View file improved.min.data ``.
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+ You can view the contents of **improved.min.data ** from LAMMPS--GUI, by
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+ right-clicking on the file name in the editor and selecting the entry
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+ ``View file improved.min.data ``.
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The created **.data ** file contains all the information necessary
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to restart the simulation, such as the number of atoms, the box size,
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