Stillinger-Weber (SW) potential with user defined functions¶

This example demonstrates the (ab)use of the modified embedded atom method (MEAM) potential routine together with user defined functions to create a Stillinger-Weber potential. The potential form and parameters have been taken from [StiWeb84]. The example also illustrates the use of XML Inclusions. Note that the potential is merely evaluated for a couple of simple lattice structures and none of the parameters are fitted.

Location¶

examples/potential_SW

Input files¶

• main.xml: main input file

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20  Stillinger and Weber, Phys. Rev. B, v. 31, p. 5262, (1985) medium Si 
• potential.xml: potential parameter set (included in main input file via XML Inclusions)

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72  3.77118 r A*epsilon*(B*(sigma/r)^(p) - (sigma/r)^(q)) * exp(sigma/(r-a*sigma)) A*exp(sigma/(r - a*sigma))*epsilon* (-((B*p*sigma*(sigma/r)^(-1 + p))/r^2) + (q*sigma*(sigma/r)^(-1 + q))/r^2) - (A*exp(sigma/(r - a*sigma))*epsilon*sigma*(B*(sigma/r)^p - (sigma/r)^q))/(r - a*sigma)^2 2.1683 2.0951 1.80 4.0 0.0 7.049556277 0.6022245584 rho rho 1 3.771179 r exp(gamma*sigma/(r-a*sigma)) -gamma * sigma * exp(gamma*sigma/(r-a*sigma)) / (r - a*sigma)^2 2.0951 1.20 1.80 costheta lambda * epsilon * (costheta - costheta0)^2 lambda * epsilon * 2 * (costheta - costheta0) 2.1683 21.0 -0.333333333333 
• structures.xml: input structures (included in main input file via XML Inclusions)

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46  Si 4.14 Si 3.24 Si 5.43 

Output (files)¶

• The final properties (as well as parameters) are written to standard output.

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 This is program version 0.1.6 Reading job file main.xml ------------------------------------------------------- Parsing input file(s) ------------------------------------------------------- ------------------------------------------------------- Computing structure properties Structure 'A1 (fcc)': total-energy: -3.94031 eV atomic-energy: -3.94031 eV/atom total-volume: 17.8242 A^3 atomic-volume: 17.8242 A^3/atom Structure 'A2 (bcc)': total-energy: -4.05556 eV atomic-energy: -4.05556 eV/atom total-volume: 17.0819 A^3 atomic-volume: 17.0819 A^3/atom Structure 'A4 (diamond)': total-energy: -8.6732 eV atomic-energy: -4.3366 eV/atom total-volume: 40.0468 A^3 atomic-volume: 20.0234 A^3/atom ------------------------------------------------------- -------------------------------------------------------