kB=1. #8.9*10.**(-5.)  #eV/K
D=0.2  #eV

A=1.
B=.1
C=0.
E=10.

s01=100.
s02=.1


S1(x)=A*x
S2(x)=C-E*D/x

sig1(x)=1./(1./s01+B*x)
sig2(x)=s02*exp(-D/(2.*kB*x))

set xrange[0:200]

p (S1(x)*sig1(x)+S2(x)*sig2(x) ) / (sig1(x)+sig2(x)) w l

#fit [14.5:59.] ((-(kBJ/e+D/x)*dl2 +(1./x)*de2 ) *10.**3) 'Sun_FeAs2_B.dat' u 1:(-$2) via dl2