1 | /* LamellarCaille kernel - allows for name changes of passed parameters ... |
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2 | |
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3 | */ |
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4 | |
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5 | static double |
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6 | Iq(double qval, |
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7 | double del, |
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8 | double fp_Nlayers, |
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9 | double dd, |
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10 | double Cp, |
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11 | double sld, |
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12 | double solvent_sld) |
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13 | { |
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14 | int Nlayers = (int)(fp_Nlayers+0.5); //cast to an integer for the loop |
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15 | double contr; //local variables of coefficient wave |
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16 | double inten,Pq,Sq,alpha,temp,t2; |
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17 | //double dQ, dQDefault, t1, t3; |
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18 | // from wikipedia 0.577215664901532860606512090082402431042159335 |
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19 | const double Euler = 0.577215664901533; // Euler's constant, increased sig figs for new models Feb 2015 |
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20 | //dQDefault = 0.0; //[=] 1/A, q-resolution, default value |
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21 | //dQ = dQDefault; // REMOVED UNUSED dQ calculations for new models Feb 2015 |
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22 | |
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23 | contr = sld - solvent_sld; |
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24 | |
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25 | Pq = 2.0*contr*contr/qval/qval*(1.0-cos(qval*del)); |
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26 | |
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27 | Sq = 0.0; |
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28 | for (int ii=1; ii < Nlayers; ii++) { |
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29 | temp = 0.0; |
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30 | alpha = Cp/4.0/M_PI/M_PI*(log(M_PI*ii) + Euler); |
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31 | //t1 = 2.0*dQ*dQ*dd*dd*alpha; |
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32 | t2 = 2.0*qval*qval*dd*dd*alpha; |
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33 | //t3 = dQ*dQ*dd*dd*ii*ii; |
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34 | |
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35 | temp = 1.0 - (double)ii / (double)Nlayers; |
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36 | //temp *= cos(dd*qval*ii/(1.0+t1)); |
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37 | temp *= cos(dd*qval*ii); |
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38 | //temp *= exp(-1.0*(t2 + t3)/(2.0*(1.0+t1)) ); |
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39 | temp *= exp(-t2/2.0); |
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40 | //temp /= sqrt(1.0+t1); |
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41 | |
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42 | Sq += temp; |
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43 | } |
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44 | |
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45 | Sq *= 2.0; |
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46 | Sq += 1.0; |
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47 | |
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48 | inten = 2.0*M_PI*Pq*Sq/(dd*qval*qval); |
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49 | |
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50 | inten *= 1.0e-04; // 1/A to 1/cm |
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51 | |
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52 | return(inten); |
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53 | } |
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54 | |
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