MDS User Manual

General Remarks

This Java-Applet has been created with one of the great tools which computer scientists created for us. That means that it is portable to any surrounding and works different or not whereever you try it. Hence this is a rather tentative user manual. But we ensure you that if you try hard enough, you can always find a platform where one special detail works as described in this manual. Go ahead!

Main Window

Click in the applet part of the MDS-window to get to the main window.


The context-menu opens when you press the right mouse button or THE mouse button while you hold down the CTRL- (or "Shift"-?) key.

Start, Stop, Pause, Continue see the corresponding buttons below
Print Prints the 3D graph. Works only in the Pause mode (if it works!).
Arrange windows Arranges the output-windows (on some browsers!).
Bring windows to top Sets the output-windows in front of the main window.
Show in frame Shows the simulation in an resizable window.


Start Opens a dialog to set the start-parameters. "Ok" starts the simulation.
Stop Resets the program completely: all output is lost! The output-windows are closed.
Pause Pauses the simulation (e.g. to print results)
Continue Resumes a paused simulation.
Settings Opens the window "Settings" (which contains a pop-up menu to open the other output-windows9.

3D Graph:

You can turn the simulation-cube around the x and y axes by dragging it with the mouse. (On some browsers also the arrow-keys might work).

The atoms are shown in different size and colors depending on their z-position. The minimal size is 5 pixels.

Setting the Start Values

The values are filled into the input-fields or chosen from the pop-up menus on the right of the fields.

Algorithm Leapfrog-Verlet
Algorithm for the integration of Newtons's equations
Priority 1 bis 9 Priority for the applet. Use a lower priority if the response of the system is slow.
Atom Neon
Ideal gas
Preset atomic values for a few cases.
Atoms > 1 Number of atoms.
Distribution Cubic primitiv
Cubic body-centered
Cubic face-centered
Start distribution of the atoms. The face- and the body-centered lattice are not yet implemented.
Comment string Comment for the present simulation.
Output file string Name of the output-file (if supported on your system).
Interval > 0; 0 no output Output interval to file in steps.
Start values Pop-up menu to select certain phase points dependent on the atom
Temperature > 0 Temperature in Kelvin.
Density > 0 Density in mol/m3
Time step .10-14 Time step in s.
Cutoff radius > 2.5 Cutoff radius in sigma units.

Customized Atom Parameters:

Name String Name of atom.
Mass > 0 Atomic mass in atomic mass units (amu)
Epsilon >= 0 Potential depth in J.
Sigma >= 0 Collisional distance in m.

Additional remarks

Atom Using "Edit" or the entry "Customized" the atomic parameters may be changed.
Comment, Output file, Interval For saving data in a file on disk. The browser might ask you for lower security to save the data (does not work on all systems).

Some thousand simulation steps might need several Mbytes!

Benchmark Starts a 5s benchmark-calculation for the parameters chosen. As a result you get the number of steps per second performed on your computer under the given conditions.

The window "Settings"

Update frequency Update frequency of the output-windows.
Set temperature Resets the temperature to the value in the input-field. The user should reset the temperature repeatedly until equilibrium is reached. The values in the accumulator-window are also reset.
Window To select and show one of the other output-windows.

The window "Start Values"

Shows the start-parameters. "Show" gives the atomic data.

The window "Results"

Shows the results of the present step. The pop-up menu at the bottom together with the button "Show" graphs in a new window the selected property versus time.

Property vs. time graph

The last 100 steps are drawn on the right side of the red bar, while all the previous steps are shown in a compressed form on the left side. Pressing the right mouse button or THE mouse button while holding down the "Shift"-key restarts the graph.

The window "Accumulators"

Shows the accumulator values divided by the number of steps, i.e. the average values (since the last reset). "Reset accumulator" resets the accumulators to 0. The pop-up menu at the bottom together with the button "Show" graphs in a new window a histogram of the one- or three-dimensional velocity distribution.