42 lines
1.7 KiB
Plaintext
42 lines
1.7 KiB
Plaintext
Additional information for pair style nb3b/screened example.
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This input uses the BMP potential (Bertani, M., Menziani, M. C.,
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& Pedone, A. (2021). Improved empirical force field for multicomponent
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oxide glasses and crystals. Physical Review Materials, 5(4), 045602).
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The interatomic potential is obtained by mixing coulombic interactions
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with other two-body functions (modified Morse and Buckingham), with a
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three-body interaction (screened harmonic function).
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The modified Morse is introduce with Tables and it is combined with
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Buckingham and coul/dsf to complete the two-body force field.
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The three-body interaction is computed with pair style nb3b/screened
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only for P-O-P angle. With the pair_coeff command the atom types
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involved in the three-body potential are specified:
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pair_coeff * * nb3b/screened PSiO.nb3b.screened P NULL O
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And they appear in the same order as in the data file:
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type 1: P;
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type 2: Na, not involved in the three body so indicated as NULL;
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type 3: O.
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In the potential file PSiO.nb3b.screened there are the parameters of
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all permutations of the required atom types. In the example, also
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parameters for Si permutations appear but they are not employed in
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the current case.
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# i j k K theta0 rho cutoff
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O P P 32.5 109.47 1.0 3.3
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O P Si 60.0 109.47 1.0 0.000
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O P O 0.000 0.000 1.0 0.000
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O Si P 60.0 109.47 1.0 0.000
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O Si Si 12.5 109.47 1.0 3.3
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(...)
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The rho value must be always higher than 0.0. Cutoff and rho are extracted
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only from symmetric interactions (e.g. O P P, O Si Si), because of that
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you do not need to specify those values for the asymmetric interactions
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(e.g. O P Si and O Si P).
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