1 // ******************************************************************************
2 //
3 // Title: Force Field X.
4 // Description: Force Field X - Software for Molecular Biophysics.
5 // Copyright: Copyright (c) Michael J. Schnieders 2001-2025.
6 //
7 // This file is part of Force Field X.
8 //
9 // Force Field X is free software; you can redistribute it and/or modify it
10 // under the terms of the GNU General Public License version 3 as published by
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12 //
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15 // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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19 // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
20 // Place, Suite 330, Boston, MA 02111-1307 USA
21 //
22 // Linking this library statically or dynamically with other modules is making a
23 // combined work based on this library. Thus, the terms and conditions of the
24 // GNU General Public License cover the whole combination.
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36 //
37 // ******************************************************************************
38 package ffx.numerics.multipole;
39
40 import static ffx.numerics.multipole.TholeTensorGlobal.tholeSource;
41
42 /**
43 * The TholeTensorQI class computes derivatives of Thole damping via recursion to order <= 4 for
44 * Cartesian multipoles in a quasi-internal frame.
45 *
46 * @author Michael J. Schnieders
47 * @see <a href="http://doi.org/10.1142/9789812830364_0002" target="_blank"> Matt Challacombe, Eric
48 * Schwegler and Jan Almlof, Modern developments in Hartree-Fock theory: Fast methods for
49 * computing the Coulomb matrix. Computational Chemistry: Review of Current Trends. pp. 53-107,
50 * Ed. J. Leczszynski, World Scientifc, 1996. </a>
51 * @since 1.0
52 */
53 public class TholeTensorQI extends CoulombTensorQI {
54
55 /**
56 * Thole damping parameter is set to min(pti,ptk)).
57 */
58 private double thole;
59
60 /**
61 * AiAk parameter = 1/(alphaI^6*alphaK^6) where alpha is polarizability.
62 */
63 private double AiAk;
64
65 /**
66 * Constructor for TholeTensorQI.
67 *
68 * @param order Tensor order.
69 * @param thole Thole damping parameter is set to min(pti,ptk)).
70 * @param AiAk parameter = 1/(alphaI^6*alphaK^6) where alpha is polarizability.
71 */
72 public TholeTensorQI(int order, double thole, double AiAk) {
73 super(order);
74 this.thole = thole;
75 this.AiAk = AiAk;
76 this.operator = Operator.THOLE_FIELD;
77
78 // Source terms are currently defined up to order 4.
79 assert (order <= 4);
80 }
81
82 /**
83 * Set Thole damping parameters
84 *
85 * @param thole a double.
86 * @param AiAk a double.
87 */
88 public void setThole(double thole, double AiAk) {
89 this.thole = thole;
90 this.AiAk = AiAk;
91 }
92
93 /**
94 * Check if the Thole damping is exponential is greater than zero (or the interaction can be
95 * neglected).
96 *
97 * @param r The separation distance.
98 * @return True if -thole*u^3 is greater than -50.0.
99 */
100 public boolean checkThole(double r) {
101 return TholeTensorGlobal.checkThole(thole, AiAk, r);
102 }
103
104 /**
105 * Generate source terms for the Challacombe et al. recursion.
106 *
107 * @param T000 Location to store the source terms.
108 */
109 protected void source(double[] T000) {
110 // Compute the normal Coulomb auxiliary term.
111 super.source(T000);
112
113 // Add the Thole damping terms: edamp = exp(-thole*u^3).
114 tholeSource(thole, AiAk, R, false, T000);
115 }
116
117 }