COMPOUND

    defines a compound, alloy or mixture, made of several materials, or even a
    mixture of different isotopes

    See also ASSIGNMAt, CORRFACT, LOW-MAT, MATERIAL, MAT-PROP

     If 
WHAT(1)
 > 0.0 and 
WHAT(2)
 > 0.0 :
        
WHAT(1)
 = atom relative content of first material in the compound
        
WHAT(2)
 = index (or name) of first material

     If 
WHAT(1)
 < 0.0 and 
WHAT(2)
 > 0.0 :
      |
WHAT(1)
| = mass fraction of first material in the compound
       
WHAT(2)
  = index (or name) of first material

     If 
WHAT(1)
 < 0.0 and 
WHAT(2)
 < 0.0 :
      |
WHAT(1)
| = volume fraction of first material in the compound
      |
WHAT(2)
| = index (or name) of first material

     No default

     In a similar way, 
WHAT(3)
 and 
WHAT(4)
 refer to the second material in the
     compound, 
WHAT(5)
 and 
WHAT(6)
 to the third one.

     
SDUM
    = name of the compound

     
Default
 (option COMPOUND not requested): no compound is defined

     For more than three materials in the same compound, add as many COMPOUND
     cards with the same 
SDUM
 name as needed (but the maximum number of
     components per compound is 80, and the maximum total number of components
     is 2400).

     
Notes:
         1) Option COMPOUND must always be used in conjunction with a MATERIAL
            card having the same 
SDUM
 name (see MATERIAL). MATERIAL cards used
            for this purpose provide the density of the compound, its material
            number and name (
WHAT(1)
 and 
WHAT(2)
 of the MATERIAL option, namely
            atomic number and weight, are ignored).

         2) The order of MATERIAL and COMPOUND cards is irrelevant.

         3) The atom (or molecule) content, mass fraction or volume fraction
            need only to be given on a relative basis (normalisation is done
            automatically by the program).

         4) Partial pressures of an (ideal) gas are equivalent to molecule
            fractions and also to volume fractions.

         5) If a compound is defined by volume fractions of the components
            (either elements or compounds themselves - see Note 8 below for
            recursive definitions), FLUKA internally calculates the atomic
            densities of each component using the densities indicated in the
            respective MATERIAL cards: in this case, therefore, (and only in
            this case), it is important that these correspond to the actual
            densities.

         6) Isotopic compositions other than natural can be defined by the
            COMPOUND option too.

         7) When using the LOW-NEUT option (explicitly or by default set by the
            DEFAULTS option), a special data set containing low-energy neutron
            cross sections for each material used must be available. The data
            sets are combined in a single file, delivered with the FLUKA program
            (logical input unit LUNXSC, = 9). Each low-energy neutron data set is
            identified either by name (if equal to a FLUKA name and unique or
            first with that name), or/and by one or more identifiers given with
            a card LOW-MAT when necessary to remove ambiguity.
            In the case of a composite material defined by a COMPOUND option,
            two possibilities are allowed (see LOW-MAT):
              a - to associate the FLUKA material with a pre-mixed neutron data
                set. In this case interactions take place with individual nuclei
                at high energy, while average cross sections are used for
                low-energy neutrons. Note that no pre-mixed neutron data set is
                yet available (at the moment the standard sets contain pure
                elements only).
              b - to associate the FLUKA material with several elemental neutron
                data sets (one per component element). In this case both
                high-energy and low-energy neutron interactions take place with
                individual nuclei. This is the only possibility at present but
                it may change in the future.

         8) Recursion is allowed, i.e. the components of a composite material
            can be composite materials. The depth of recursion is only limited
            by the size of the internal arrays (in case of overflow a message
            is issued and the job is terminated). Different levels of recursion
            can use different units in the definition of the component fractions
            (atoms, mass or volume fractions). Note, however, that if a compound
            is put together from different composite molecules, the atomic and
            molecular fractions have to be given without normalisation (use the
            chemical formulae directly).
            What follows is an example (for a number-based input) of a simple
            compound BOOZE containing 50 weight percent of water and 50 of
            ethanol.

 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
 MATERIAL         1.0       0.0  .0000899       3.0       0.0      0.0 HYDROGEN
 MATERIAL         6.0       0.0       2.0       4.0       0.0      0.0 CARBON
 MATERIAL         8.0       0.0   0.00143       5.0       0.0      0.0 OXYGEN
 MATERIAL         0.0       0.0       1.0      20.0       0.0      0.0 WATER
 MATERIAL         0.0       0.0    0.7907       7.0       0.0      0.0 ETHANOL
 MATERIAL         0.0       0.0    0.9155       8.0       0.0      0.0 BOOZE
 COMPOUND         2.0       3.0       1.0       5.0       0.0      0.0 WATER
 COMPOUND         2.0       4.0       6.0       3.0       1.0      5.0 ETHANOL
 COMPOUND       -50.0      20.0     -50.0       7.0       0.0      0.0 BOOZE
 *   Note that in the above example materials 4, 5, 7 and 8 have been defined
 *   overriding the default FLUKA material numbers.This is only allowed in
 *   an explicitly number-based input, declared as such with 
WHAT(4)
 = 4.0 in
 *   command GLOBAL.

     The same example, in a name-based input, could be:

 MATERIAL         1.0       0.0  .0000899       0.0       0.0      0.0 HYDROGEN
 MATERIAL         6.0       0.0       2.0       0.0       0.0      0.0 CARBON
 MATERIAL         8.0       0.0   0.00143       0.0       0.0      0.0 OXYGEN
 MATERIAL         0.0       0.0       1.0       0.0       0.0      0.0 WATER
 MATERIAL         0.0       0.0    0.7907       0.0       0.0      0.0 ETHANOL
 MATERIAL         0.0       0.0    0.9155       0.0       0.0      0.0 BOOZE
 COMPOUND         2.0  HYDROGEN       1.0    OXYGEN       0.0      0.0 WATER
 COMPOUND         2.0    CARBON       6.0  HYDROGEN       1.0   OXYGEN ETHANOL
 COMPOUND       -50.0     WATER     -50.0   ETHANOL       0.0      0.0 BOOZE

     Example of how COMPOUND is commonly used to define a mixture (concrete).
     In a number-based input:

 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
 * definition of material 27 (concrete) as compound:  H (1%), C(0.1%),
 * O(52.9107%), Na(1.6%), Mg(0.2%), Al(3.3872%), Si(33.7021%), K(1.3%),
 * Ca(4.4%), Fe(1.4%)
 MATERIAL        19.0       0.0     0.862      26.0       0.0      0.0 POTASSIU
 MATERIAL         0.0       0.0      2.35      27.0       0.0       0. CONCRETE
 COMPOUND       -0.01       3.0    -0.001       6.0 -0.529107       8. CONCRETE
 COMPOUND      -0.016      19.0    -0.002       9.0 -0.033872      10. CONCRETE
 COMPOUND   -0.337021      14.0    -0.013      26.0    -0.044      21. CONCRETE
 COMPOUND      -0.014      11.0
 *   In the above example, elements 3 (hydrogen), 6 (carbon), 8 (oxygen),
 *   9 (magnesium), 10 (aluminium), 11 (iron), 14 (silicon), 19 (sodium) and
 *   21 (calcium) are not defined because the corresponding pre-defined FLUKA
 *   materials are used (see 5}). Potassium is not pre-defined, therefore it is
 *   assigned a new numbers 26 (that keeps the numbering sequence continuous,
 *   since the last FLUKA pre-defined material has number 25). The name is
 *   chosen to correspond with the potassium neutron cross section data set.
 *   (Chap. 10})

     The same example, in a name-based input:

 MATERIAL        19.0       0.0     0.862       0.0       0.0      0.0 POTASSIU
 MATERIAL         0.0       0.0      2.35       0.0       0.0       0. CONCRETE
 COMPOUND       -0.01  HYDROGEN    -0.001    CARBON -0.529107   OXYGEN CONCRETE
 COMPOUND      -0.016    SODIUM    -0.002  MAGNESIU -0.033872 ALUMINUM CONCRETE
 COMPOUND   -0.337021   SILICON    -0.013  POTASSIU    -0.044  CALCIUM CONCRETE
 COMPOUND      -0.014      IRON

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