RandSpg: Generate Random Crystals with Specific Spacegroups

A sample input is given in the text area below.
Change it around as needed and click "submit" when you are ready for RandSpg to generate the crystal structures!

First line is a comment line

# Anything to the right of a hash is a comment

# Composition is set by atomic symbols followed by number as such:
composition            = Mg4Al2

# Which spacegroups to generate are set as follows (hyphens and commas work)
spacegroups            = 1-6, 10, 25

# lattice mins and maxes set constraints on the lattice to be generated.
# Distances are in Angstroms and angles are in degrees.
#                           a,    b,    c, alpha,  beta, gamma
latticeMins            =  3.0,  3.0,  3.0,  60.0,  60.0,  60.0
latticeMaxes           = 10.0, 10.0, 10.0, 120.0, 120.0, 120.0

# minVolume and maxVolume specify constraints on the volume in Angstroms
# If the volume is not within this range, it will be rescaled so that it is
# If you remove minVolume or specify it to be -1, there will be no minVolume
# Same goes for maxVolume
minVolume              = 450
maxVolume              = 500

# numOfEachSpgToGenerate tells us how many crystals of each spg to generate
numOfEachSpgToGenerate = 3

# For advanced users: by default, the program will only generate a spacegroup
# for a crystal if it can use the most general Wyckoff position at least
# once. This is because the spacegroup is not guaranteed if the most
# general Wyckoff position is not used at least once. The user, however,
# may turn off that option here by setting it to false.
# If this is the case, more compositions may be generated for a particular
# spacegroup, but they may not be the correct spacegroup (about a 50 or 60%
# chance overall - but it differs with each spacegroup)

#forceMostGeneralWyckPos = false

# For advanced users: this allows us to force an element to be assigned
# to a specific Wyckoff position. If you wish to force an element to be in
# the same Wyckoff position multiple times, just repeat the tag multiple times
# i. e. add 'forceWyckPos Mg = a' on as many lines as you want to force the
# Wyckoff position

#forceWyckPos Mg        = a

# We can set minimum radii (Angstroms) for individual atoms

#setRadius Ti           = 0.5

# Or for all atoms. A min radius for an individual atom trumps this one
# If the default min radius of the atom is less than this input value, then
# the min radius of that atom is set to be this value
# Value is in Angstroms

#setMinRadii            = 0.3

# This scaling factor will scale all radii that were not explicity set
# The new radii are equal to (radius * scalingFactor)
# This is particularly useful when changing the pressure of a crystal

scalingFactor          = 0.5

# This sets the maximum number of attempts to generate any given spacegroup
maxAttempts            = 50

# Verbosity indicates how much output to generate in the log file (the log
# file will be prepended to the html output)
# 'n' is no output, 'r' is regular output, and 'v' is verbose output
verbosity              = r

Notes:

Since this program is running on a server that runs other programs, it may run too slow (depending on the settings) and time out. If you'd like to run it at full speed, please obtain and compile the program from the Github repository and run the executable on your local computer.
The POSCAR format is specified here.
If you wish to visualize the crystal using the Avogadro molecular editor, copy the POSCAR of the crystal, click the "Crystallography" menu at the top of Avogadro, and select "Import Crystal from Clipboard...".
If you wish to use another format, you may convert it using OpenBabel.

About:

RandSpg is an algorithm developed by Patrick Avery. RandSpg generates random crystals of specific spacegroups and allows the user to specify a lot of information such as minimum interatomic distances, volume constraints, etc. The source code is available under the "New" BSD open source license and may be viewed at its Github repository.

If you encounter any bugs, please email me at psavery@buffalo.edu