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
11 // the Free Software Foundation.
12 //
13 // Force Field X is distributed in the hope that it will be useful, but WITHOUT
14 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
15 // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
16 // details.
17 //
18 // You should have received a copy of the GNU General Public License along with
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.
25 //
26 // As a special exception, the copyright holders of this library give you
27 // permission to link this library with independent modules to produce an
28 // executable, regardless of the license terms of these independent modules, and
29 // to copy and distribute the resulting executable under terms of your choice,
30 // provided that you also meet, for each linked independent module, the terms
31 // and conditions of the license of that module. An independent module is a
32 // module which is not derived from or based on this library. If you modify this
33 // library, you may extend this exception to your version of the library, but
34 // you are not obligated to do so. If you do not wish to do so, delete this
35 // exception statement from your version.
36 //
37 // ******************************************************************************
38 package ffx.numerics.multipole;
39
40 import static ffx.numerics.multipole.EwaldTensorGlobal.fillEwaldSource;
41 import static ffx.numerics.multipole.EwaldTensorGlobal.initEwaldSource;
42
43 /**
44 * The EwaldTensorQI class computes derivatives of erfc(<b>r</b>)/|<b>r</b>| via recursion to
45 * arbitrary order for Cartesian multipoles in a quasi-internal frame.
46 *
47 * @author Michael J. Schnieders
48 * @see <a href="http://doi.org/10.1142/9789812830364_0002" target="_blank"> Matt Challacombe, Eric
49 * Schwegler and Jan Almlof, Modern developments in Hartree-Fock theory: Fast methods for
50 * computing the Coulomb matrix. Computational Chemistry: Review of Current Trends. pp. 53-107,
51 * Ed. J. Leczszynski, World Scientifc, 1996. </a>
52 * @since 1.0
53 */
54 public class EwaldTensorQI extends CoulombTensorQI {
55
56 /**
57 * These are the "source" terms for the recursion for the screened Coulomb operator erfc(R)/R.
58 */
59 private final double[] ewaldSource;
60
61 /**
62 * The Ewald convergence parameter.
63 */
64 private final double beta;
65
66 /**
67 * Constructor for EwaldTensorQI.
68 *
69 * @param order Tensor order.
70 * @param beta The Ewald convergence parameter.
71 */
72 public EwaldTensorQI(int order, double beta) {
73 super(order);
74 this.beta = beta;
75 operator = Operator.SCREENED_COULOMB;
76
77 // Auxiliary terms for screened Coulomb (Sagui et al. Eq. 2.28)
78 ewaldSource = new double[o1];
79 initEwaldSource(order, beta, ewaldSource);
80 }
81
82 /**
83 * Generate source terms for the Ewald Challacombe et al. recursion.
84 *
85 * @param T000 Location to store the source terms.
86 */
87 @Override
88 protected void source(double[] T000) {
89 // Generate source terms for real space Ewald summation.
90 if (beta > 0.0) {
91 fillEwaldSource(order, beta, ewaldSource, R, T000);
92 } else {
93 // For beta = 0, generate tensors for the Coulomb operator.
94 super.source(T000);
95 }
96 }
97
98 }