| 1 | subroutine gelfit |
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| 2 | * SHIBAYAMA-GEISSLER TWO-LENGTH SCALE SCATTERING FUNCTION FOR GELS |
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| 3 | |
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| 4 | * See Sibayama, Tanaka & Han, J Chem Phys, (1992), 97(9), 6829-6841 |
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| 5 | * or Mallam, Horkay, Hecht, Rennie & Geissler, Macromol, (1991), 24, 543 |
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| 6 | |
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| 7 | include 'frills_sources:function.inc' |
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| 8 | |
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| 9 | real*8 lscale,gscale,zeta,rg,df,bkgd |
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| 10 | real*8 a,b,c,d,e |
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| 11 | |
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| 12 | lscale=p(1) |
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| 13 | gscale=p(2) |
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| 14 | * ZETA IS CORRELATION LENGTH IN LORENTZIAN |
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| 15 | zeta=p(3) |
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| 16 | * RG IS THE RADIUS OF GYRATION OF THE INHOMOGENEITIES |
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| 17 | rg=p(4) |
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| 18 | * DF IS THE FRACTAL EXPONENT |
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| 19 | * SCATTERING LAW REDUCES TO PURE LORENZTIAN IF DF=2 |
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| 20 | df=p(5) |
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| 21 | bkgd=p(6) |
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| 22 | |
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| 23 | if (df.le.0) then |
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| 24 | write(6,*)' ' |
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| 25 | write(6,*)'The Scaling Exponent must be >=0' |
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| 26 | write(6,*)'Will set to 2.' |
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| 27 | write(6,*)' ' |
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| 28 | df=2. |
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| 29 | end if |
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| 30 | |
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| 31 | do j=1,nv |
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| 32 | * LORENTZIAN TERM |
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| 33 | a=x(j)*x(j)*zeta*zeta |
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| 34 | b=(1.+(((df+1.)/3.)*a)) |
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| 35 | c=b**(df/2.) |
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| 36 | * EXPONENTIAL TERM |
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| 37 | d=x(j)*x(j)*rg*rg |
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| 38 | e=-1.*(d/3.) |
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| 39 | f=dexp(e) |
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| 40 | * SCATTERING LAW |
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| 41 | ycal(j)=(lscale/c)+(gscale*f)+bkgd |
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| 42 | end do |
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| 43 | |
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| 44 | return |
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| 45 | end |
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