# Fityk 0.7.8
## this script is an example of Pawley method for powder pattern in Fityk

# it is very complicated, but there is not simpler method to do it
# at this moment. In future there will be no need to write any equations.

# Load data file from directory of this script (SiC+Zn data)
@0 < _EXECUTED_SCRIPT_DIR_/SiC_Zn.dat

# background was obtained by clicking on plot in "background mode"
Y = y - spline[20.4823,43.3474,  28.004,24.3128,  31.4412,23.6984,  33.7911,36.0138,  38.6477,30.5403,  49.9335,17.263,  65.1888,17.968,  79.5965,22.1979, 98.9835,23.6079](x)

A = 31 < x < 90 # only data with 2theta greater then 31.0 are active

# Used wavelength is known and we do not want to fit it.
# If you would like to fit wavelength, put '~' before the number
$lambda = 1.54051 # Cu Ka1

#initial lattice parameters
$sic_a = ~4.35 #cubic SiC
$zn_a = ~2.67; $zn_c = ~4.924 #hexagonal Zn

# here are well known formulae for peak positions:
#1/d = sqrt(h^2 + k^2 + l^2) / a # for cubic phase
#1/d = sqrt(4./3. * (h^2 + k^2 + h*k) / a^2 + l^2 / c^2) # for hexagonal phase
#peak_center = 2 * asin((1/d) / 2 * lambda) [in RAD, must be converted to DEG]


# peak hkl=(220) of SiC
$c_sic220 = 360/pi * asin(sqrt(2^2+2^2+0) / $sic_a / 2 * $lambda)
set guess-at-center-pm = 1
%sic220 = guess PseudoVoigt center=$c_sic220

# Zn (002) 
$c_zn002 = 360/pi * asin(sqrt(4/3 * (0+0+0*0) / $zn_a^2 + 2^2/$zn_c^2 ) / 2 * $lambda)
%zn002 = guess PseudoVoigt center=$c_zn002

# SiC (111) 
$c_sic111 = 360/pi * asin(sqrt(1^2+1^2+1^2) / $sic_a / 2 * $lambda)
%sic111 = guess PseudoVoigt center=$c_sic111

# Zn (100)
$c_zn100 = 360/pi * asin(sqrt(4/3 * (1^2+0+1*0) / $zn_a^2 + 0/$zn_c^2 ) / 2 * $lambda)
%zn100 = guess PseudoVoigt center=$c_zn100

# Zn (101)
$c_zn101 = 360/pi * asin(sqrt(4/3 * (1^2+0+1*0) / $zn_a^2 + 1^2/$zn_c^2 ) / 2 * $lambda)
%zn101 = guess PseudoVoigt center=$c_zn101

# Zn (102)
$c_zn102 = 360/pi * asin(sqrt(4/3 * (1^2+0+1*0) / $zn_a^2 + 2^2/$zn_c^2 ) / 2 * $lambda)
%zn102 = guess PseudoVoigt center=$c_zn102


#after adding a few peaks, it can be a good idea to fit it, to obtain
#better approximation of lattice parameters
fit 10 

# Zn (103)
$c_zn103 = 360/pi * asin(sqrt(4/3 * (1^2+0+1*0) / $zn_a^2 + 3^2/$zn_c^2 ) / 2 * $lambda)
%zn103 = guess PseudoVoigt center=$c_zn103

# Zn (110) 
$c_zn110 = 360/pi * asin(sqrt(4/3 * (1^2+1^2+1*1) / $zn_a^2 + 0^2/$zn_c^2 ) / 2 * $lambda)
%zn110 = guess PseudoVoigt center=$c_zn110

# Zn (112) 
$c_zn112 = 360/pi * asin(sqrt(4/3 * (1^2+1^2+1*1) / $zn_a^2 + 2^2/$zn_c^2 ) / 2 * $lambda)
%zn112 = guess PseudoVoigt center=$c_zn112

# Zn (200) 
$c_zn200 = 360/pi * asin(sqrt(4/3 * (2^2+0^2+2*0) / $zn_a^2 + 0^2/$zn_c^2 ) / 2 * $lambda)
%zn200 = guess PseudoVoigt center=$c_zn200

# we constrain width and shape of this small peak (200)
%zn200.shape = %zn112.shape
%zn200.hwhm = %zn112.hwhm

# Zn (201) 
$c_zn201 = 360/pi * asin(sqrt(4/3 * (2^2+0^2+2*0) / $zn_a^2 + 1^2/$zn_c^2 ) / 2 * $lambda)
%zn201 = guess PseudoVoigt center=$c_zn201

# SiC (311)
$c_sic311 = 360/pi * asin(sqrt(3^2+1^2+1^2) / $sic_a / 2 * $lambda)
%sic311 = guess PseudoVoigt center=$c_sic311

Z = Constant(~0.) #zero-shift

# fit   #running default fitting method (Lev-Mar)
       #'lambda' that you can see in output window is a parameter used by
       # fitting method, not wavelength.