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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.
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38  package ffx.numerics.multipole;
39  
40  import jdk.incubator.vector.DoubleVector;
41  
42  import static ffx.numerics.multipole.TholeTensorGlobalSIMD.tholeSource;
43  
44  /**
45   * The TholeTensorQI class computes derivatives of Thole damping via recursion to order <= 4 for
46   * Cartesian multipoles in a quasi-internal frame.
47   *
48   * @author Michael J. Schnieders
49   * @see <a href="http://doi.org/10.1142/9789812830364_0002" target="_blank"> Matt Challacombe, Eric
50   * Schwegler and Jan Almlof, Modern developments in Hartree-Fock theory: Fast methods for
51   * computing the Coulomb matrix. Computational Chemistry: Review of Current Trends. pp. 53-107,
52   * Ed. J. Leczszynski, World Scientifc, 1996. </a>
53   * @since 1.0
54   */
55  public class TholeTensorQISIMD extends CoulombTensorQISIMD {
56  
57    /**
58     * Thole damping parameter is set to min(pti,ptk)).
59     */
60    private DoubleVector thole;
61  
62    /**
63     * AiAk parameter = 1/(alphaI^6*alphaK^6) where alpha is polarizability.
64     */
65    private DoubleVector AiAk;
66  
67    /**
68     * Constructor for TholeTensorQI.
69     *
70     * @param order Tensor order.
71     * @param thole Thole damping parameter is set to min(pti,ptk)).
72     * @param AiAk  parameter = 1/(alphaI^6*alphaK^6) where alpha is polarizability.
73     */
74    public TholeTensorQISIMD(int order, DoubleVector thole, DoubleVector AiAk) {
75      super(order);
76      this.thole = thole;
77      this.AiAk = AiAk;
78      this.operator = Operator.THOLE_FIELD;
79  
80      // Source terms are currently defined up to order 4.
81      assert (order <= 4);
82    }
83  
84    /**
85     * Set Thole damping parameters
86     *
87     * @param thole a double.
88     * @param AiAk  a double.
89     */
90    public void setThole(DoubleVector thole, DoubleVector AiAk) {
91      this.thole = thole;
92      this.AiAk = AiAk;
93    }
94  
95    /**
96     * Check if the Thole damping is exponential is greater than zero (or the interaction can be
97     * neglected).
98     *
99     * @param r The separation distance.
100    * @return True if -thole*u^3 is greater than -50.0.
101    */
102   public boolean checkThole(DoubleVector r) {
103     return TholeTensorGlobalSIMD.checkThole(thole, AiAk, r);
104   }
105 
106   /**
107    * Generate source terms for the Challacombe et al. recursion.
108    *
109    * @param T000 Location to store the source terms.
110    */
111   protected void source(DoubleVector[] T000) {
112     // Compute the normal Coulomb auxiliary term.
113     super.source(T000);
114 
115     // Add the Thole damping terms: edamp = exp(-thole*u^3).
116     tholeSource(thole, AiAk, R, T000);
117   }
118 
119 }