Contents: 
    1) Calculation method (for mixtures)
    2) Important notice (for mixtures)
    3) Description of the input parameters


    1) Calculation method (for mixtures)
    ====================================

 <extracted from doc of cross_calc_mix>
	i) calculate attenuation mass coefficient for each elements by
	   calling cross_calc
	ii) Calculate the weight composition wi of each element in the 
	   mixture by calling parse_mixture 
	iii) The attenuation mass coefficient mu_m for the mixture is the 
	   averaged attenuation from the elements (mu_i):
		mu_m = Sum{ wi * mu_i } 
	iv) Returns the value in the correspondent units:
		UNIT=3 (cm-1) returns density*mu_m
		UNIT=2 (cm2/g) returns mu_m
		UNIT=1 (cm2) returns mu_m*(MW/NA) being MW the molecular
			weight and NA the Avogadro's number. 
		UNIT=0 (barns/at) returns mu_m*(MW/NA)*1e24
	
	The MW (molecular weight) is MW = Sum { fi * Ai), being Ai
		the atomic weight of the i-th element and fi the 
		number of atoms of the i-th type in the molecule.


    2) Important notice (for mixtures)
    ==================================


 <extracted from doc of cross_calc_mix>

	   The attenuation coefficient is dependent on 
	   the fractional weigths, so the result is independent if how the 
	   mixture is defined, either 
		i) as a function of the weight fractions 
		ii) as a molecular mixture. 
	   Therefore, water can be either defined as "H2O" (molecule) 
		or "H(0.11)O(0.89)" (weight). 	

	   However, for calculating the cross section of the mixture
		(UNIT = 0 or 1) the molecular weigth enters in the 
		calculation, and this value is different depending how the 
		mixture is defined, because DABAX does not know the molecular 
		weight, but calculates it from the mixture formula:
		For example, for water:
		   i) Molecular weight (H2O): 18.015280
		   ii)  Molecular weight (H(0.11)O(0.89)):  14.350339

		THEREFORE, FOR CROSS SECTIONS (UNIT=0,1), THE MIXTURE SHOULD BE
		DEFINED IN ITS MOLECULAR FORM (like "H2O") AND NOT IN ITS 
		WEIGHT FRACTION (like "H(0.11)O(0.89)"). 

		PLEASE NOTE THAT THE PRE-DEFINED COMPOUNDS (IN DABAX
		FILE Compounds.dat CONTAIN THE MIXTURE FORMULA, AND IN
		SOME CASES (THE COMPOUNDS OBTAINED FROM NIST DATABASE)
		THE MOLECULAR FORMULA IS NOT PRESENT (ONLY WEIGHT FORMULA)
		THEREFORE THE CROSS SECTION VALUES (UNIT=0,1) MAY BE WRONG.



    3) Description of the input parameters
    ======================================

datasets: 
	Select a DABAX file from where the Photon-Atom Cross section
	will be read. The "all" option is also available, and 
	in this case all datasets are used (useful for comparisons).

material: Select the desired material type. Three options are available:
	a) Element(formula) calculation for a single element. 
	b) Mixture(formula) calculation for a compound or a mixture. The user 
		defines the mixture formula. 
		The syntaxis is the following: string with the chemical
		formula of the compound(s) with their weight fraction between 
		parenthesis.
		Examples:
		H20
		SiO2(0.807)B2O3(0.129)Na2O(0.038)Al2O3(0.022)K2O(0.004)
		H2O(0.99)Cl2(0.01)
		H(0.11189834)O(0.88810166)
	c) Mixture(table) calculation for a compound or a mixture defined
		in the included mixture-table (from dabax file Compounds.dat)

table: Compound table, only available if the c) option in material is chosen.

formula: The element or compound or mixture formula, depending the "material"
		selection.

calculate: type the calculation magnitude. The typed word will be
		compared with the magnitude name in the DABAX file, and if 
		they match, the corresponding data are loaded. 
		The "all" option is also available, and in this case all 
		datasets are used (useful for comparisons). 

Energy [eV] grid: the abscissas values for the calculations. Two 
		options are available: 
		a) Standard, which is the energy grid defined in the 
		   DABAX file read in first place.
		b) User-defined, with the parameters described below.
		c) Single-value, with the energy to be entered in 
		   "Starting Energy [eV]" box.

Stating Energy [eV]: the initial energy value (only available if either
		b) or c) is chosen in the "Energy [eV] grid" entry.

To: the last energy value (only available if b) is chosen in the
		"Energy [eV] grid" entry.

Number of points: the number of energy points (only available if b) is 
		chosen in the "sin_theta/lambda grid" entry.

Units: the units in which the Cross Sections are presented