This is a description of the input parameters for xcrystal

DABAX f0 FILE: 
	Select a DABAX file from where the f0 component of the structure 
	factor will be read.

DABAX f1f2 FILE: Select a DABAX file from where the f1f2 components of 
	the structure factor will be read.

CRYSTAL: Select a crystal from this list of crystals.

h MILLER INDEX: obvious
k MILLER INDEX: obvious
l MILLER INDEX: obvious


TEMPERATURE FACTOR: Three possibilites:
       1) Enter the exp(-M) value (a positive value between 0 and 1)
       2) Enter the absolute temperatute in Kelvin, WITH A MINUS SIGN.
	  The minus sign tells to the code that the number entered
	  refers to a temperature and not to the full debye-waller exp(-M)
	  factor. The minus sign will not be considered for the numerial
	  calculations. 
	  In this case, the Debye-Waller factor is calculated 
	  as a function of the temperature, using a well-known approximation 
	  as a function of sin(theta/lambda)=1/(2d), temperature, atomic 
	  mass and Debye-temperature. In the case of crystal structures 
	  with more that one atomic sites, an independent Debye-Waller 
	  factor is calculated for each atomic site and then putting them 
	  together by averaging the M's. Values for atomic mass and 
	  Debye temperatures are obtained from the DABAX file
	  AtomicConstants.dat. For more info, see the documentation in the
	  function DebyeWaller.pro
       3) Enter a question mark (?). 
	  In this case, the code will perform the calculation as in 
	  point 2), but it will pop-up a window that will permit to modify 
	  the Debye-Waller ingredients (i.e., the sin(theta/lambda)=1/(2d) 
	  ratio, temperatute, atomic mass and Debye temperature). 
	  In the case of crystal structures with several atomic types, 
	  several values of atomic mass and Debye temperature should be entered.
	  The default values are taken from the DABAX file AtomicConstants.dat. 
	  The interest of this option is to allow the user to "improve"
	  the default value of the temperature factor, which is 
	  mostly "structure" dependent rather than dependent on the atomic 
	  types. For example, in the case of AlphaQuartz (SiO2), The Debye 
	  temperature of the oxygen is not defined by default in the 
	  AtomicConstants.dat DABAX file because oxigen does not exist in
	  crystalline state. Therefore the averaged value seems not realistic.
	  This option allows to customize the Debye temperatures from 
	  default (note that values of Debye temperature found in bibliography 
	  change significatively from one reference to another) and also allows
	  to enter average values of atomic mass and Debye temperature by 
	  entering identical values foe all atomic sites. 
	  Note that if values are changed in this window, they are not
	  saved for further runs, nor saved to input files like
	  xcrystal.xop. 

MOSAIC CRYSTAL: Select YES when you want "mosaic crystal", otherwise 
	"perfect crystal" is set.

GEOMETRY: select one of the four cases combining Laue and Bragg cases 
	for either diffracted or transmitted beam. Note that the 
	transmitted intensity is not implemented for mosaic crystals.

SCAN: The scanned variable for the plot. Angular and Energy scans are
	allowed. The angular variable can be: Theta, when absolute angle
	is wanted; Th-ThBragg(corrected) or angular scan with zero at
	the bragg angle corrected for refraction; Th-ThBragg or angular
	scan with zero at the bragg angle; and y is dimensionless angular
	variable defined by (for instance) in the Zachariasen book.
	In the case of angular scans the unit can be set, except in the
	case of y. Energy is always in eV.

SCAN UNITS: angular units, if angular scan is set.

MIN SCAN VALUE: min value for the scanning variable.

MAX SCAN VALUE: max value for the scanning variable.

SCAN POINTS: the number of scanning points.

FIX VALUE (E[eV]) OR Theta[deg]): Place here either the energy value of the 
	monochromatic incident photon beam (when angular scan is
	selected) or the grazing angle [in degrees] when a energy scan 
	is wanted.
	In the case of energy scan, the program can calculate
	automatically the theta angle if one inputs the energy. If this 
	option is selected, enter the Energy with a minus sign in this box.

ASYMMETRY ANGLE [deg]: the angle between the Bragg planes and the crystal 
	surface. It is 0.0 for the symmetrical Bragg case and 90.0 for 
	the symmetrical Laue case.
	This input is not present when using Mosaic crystals, which are
	always symmetrical.

CRYSTAL THICKNESS [cm]: the crystal thickness in cm

MOSAICITY [deg fwhm]: The mosaicirty of the mosaic crystal (if selected).