| Geant4 Cross Reference |
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25
26 //---------------------------------------------------------------------------
27 //
28 // ClassName: G4AtomicFormFactor
29 //
30 // Description: Contains the function for the evaluation of the atomic form
31 // factor. The tabulated data are available on IUCr website
32 //
33 // Class description:
34 //
35 // XXX
36 //
37 // 21-04-16, created by E.Bagli
38
39 #ifndef G4ATOMICFORMFACTOR_HH
40 #define G4ATOMICFORMFACTOR_HH 1
41
42 #include "G4Exp.hh"
43 #include "globals.hh"
44
45 #include <map>
46 #include <vector>
47
48 class G4AtomicFormFactor
49 {
50 public:
51 static G4AtomicFormFactor* GetManager()
52 {
53 if (s_G4AtomicFormFactorManager == nullptr) {
54 s_G4AtomicFormFactorManager = new G4AtomicFormFactor();
55 }
56 return s_G4AtomicFormFactorManager;
57 }
58
59 G4double Get(G4double kScatteringVector, G4int Z, G4int charge = 0)
60 {
61 if (loadedIndex != GetIndex(Z, charge)) {
62 LoadCoefficiencts(GetIndex(Z, charge));
63 }
64 G4double result = 0.;
65 G4double kVecOn4PiSquared =
66 (kScatteringVector / 1.e-7 / 3.1415926536) * 0.125; // (k/(4pi))/ angstrom
67 kVecOn4PiSquared = kVecOn4PiSquared * kVecOn4PiSquared; // (k/(4pi))^2
68
69 for (unsigned int i0 = 0; i0 < 4; i0++) {
70 result += theCoefficients[i0 * 2] * G4Exp(-theCoefficients[i0 * 2 + 1] * kVecOn4PiSquared);
71 }
72 result += theCoefficients[8];
73 return result;
74 }
75
76 protected:
77 G4AtomicFormFactor();
78 ~G4AtomicFormFactor() = default;
79
80 private:
81 void InsertCoefficients(G4int index, const std::vector<G4double>& aDoubleVec)
82 {
83 theCoefficientsMap.insert(std::pair<G4int, std::vector<G4double>>(index, aDoubleVec));
84 }
85
86 // LoadCoefficiencts() method allows the evaluation of the atomic form
87 // factor coefficients and the storage in theCoefficients.
88 // If theCoefficients are already correct, no need to get new ones
89 // Reference: International Tables for Crystallography (2006).
90 // Vol. C, ch. 6.1, pp. 554-595
91 // doi: 10.1107/97809553602060000600
92 // Chapter 6.1. Intensity of diffracted intensities
93 // IUCr Eq. 6.1.1.15, Coefficients Table 6.1.1.4
94 void LoadCoefficiencts(G4int index)
95 {
96 loadedIndex = index;
97 for (unsigned int i0 = 0; i0 < 9; i0++) {
98 theCoefficients[i0] = theCoefficientsMap[index][i0];
99 }
100 }
101
102 // Get() function gives back the Atomic Form Factor of the Z material
103 inline G4int GetIndex(G4int Z, G4int charge = 0) { return Z * 100 + charge; }
104
105 private:
106 inline static G4AtomicFormFactor* s_G4AtomicFormFactorManager = nullptr;
107
108 // theCoefficientsMap stores the coefficients for the form factor
109 // calculations. It can be loaded only by LoadCoefficiencts()
110 // and accessed by theCoefficients[].
111 std::map<G4int, std::vector<G4double>> theCoefficientsMap;
112 G4double theCoefficients[9];
113 G4int loadedIndex;
114 };
115 #endif
116