diff --git a/examples/prd/Si.sw b/examples/prd/Si.sw
new file mode 100644
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--- /dev/null
+++ b/examples/prd/Si.sw
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+# Stillinger-Weber parameters for various elements and mixtures
+# multiple entries can be added to this file, LAMMPS reads the ones it needs
+# these entries are in LAMMPS "metal" units:
+#   epsilon = eV; sigma = Angstroms
+#   other quantities are unitless
+
+# format of a single entry (one or more lines):
+#   element 1, element 2, element 3, 
+#   epsilon, sigma, a, lambda, gamma, costheta0, A, B, p, q, tol
+
+# Here are the original parameters in metal units, for Silicon from:
+#
+# Stillinger and Weber,  Phys. Rev. B, v. 31, p. 5262, (1985)
+#
+
+Si Si Si 2.1683  2.0951  1.80  21.0  1.20  -0.333333333333
+         7.049556277  0.6022245584  4.0  0.0 0.0