Random alloys

random_alloy gives the atoms of a system elements drawn at random in given fractions, with exact counts, for example a high-entropy alloy on a crystal.

from mdapy.build import build_crystal, random_alloy

sites = build_crystal("fcc", 3.6, repeat=(10, 10, 10))
cantor = random_alloy(sites, {"Co": 1, "Cr": 1, "Fe": 1, "Mn": 1, "Ni": 1}, seed=1)
steel = random_alloy(
    build_crystal("bcc", 2.87, repeat=(10, 10, 10)), {"Fe": 0.9, "Cr": 0.1}, seed=2
)

import numpy as np
from mdapy.visualization import render, write_png

left = render(cantor, width=600, height=600, legend=True)
right = render(steel, width=600, height=600, legend=True)
write_png("images/alloys.png", np.hstack([left, right]))

Left: the Cantor alloy CoCrFeMnNi on fcc sites, one fifth of each element. Right: Fe-10Cr on bcc sites, chromium in grey-blue.

Parameters

random_alloy(system, fractions, *, seed=None)

Name	Type	Default	Meaning
system	System		the sites, such as a crystal from build_crystal
fractions	dict of str to float64		the fraction of each element, positive; they are normalized to sum to 1
seed	int64 or numpy.random.Generator	None	the random order; the same seed gives the same alloy

Results

The system with a new element column and everything else unchanged. Each element has its fraction of the atoms rounded down, and the atoms left over go to the largest remainders, ties to the element named first: 500 atoms in three equal fractions are 167, 167 and 166.

Errors

random_alloy raises InvalidParameter without fractions, for an unknown element or for a fraction that is not positive.