graphite  LANL       EVAL-apr93 MACFARLANE                       
 ref. 4 (1994)        DIST-MAY10                       20100309   
----JENDL-4.0         MATERIAL 31                                 
-----THERMAL NEUTRON SCATTERING DATA                              
------ENDF-6 FORMAT                                               
 The data were taken from ENDF/B-VI.8.                            
  temperatures = 296, 400, 500, 600, 700, 800, 1000,              
                    1200, 1600, 2000 deg k.                       
 this evaluation was generated at the los alamos national         
 laboratory (apr 1993) using the leapr code.  the physical        
 model is very similar to the one used at general atomic          
 in 1969 to produce the original endf/b-iii evaluations           
 (see ref. 1).  tighter grids and extended ranges for alpha       
 and beta were used.  a slightly more detailed calculation        
 of the coherent inelastic scattering was generated.  of          
 course, the various constants were updated to agree with         
 the endf/b-vi evaluation of natural carbon.                      
 graphite has an hexagonal close-packed crystal structure.  the   
 lattice dynamics is represented using a model with four force    
 constants (refs.2,3).  one force constant is used to describe a  
 nearest-neighbor central force that binds two hexagonal planes   
 together, another describes a bond-bending force in an hexagonal 
 plane, the third is for bond-stretching between nearest neighbors
 in a plane, and the fourth corresponds to a restoring force      
 against bending of the hexagonal plane.  the force constants     
 were evaluated numerically using a very precise fit to the       
 high and low temperature specific heat and compressibility       
 of reactor grade graphite.  the phonon spectrum was computed     
 from this model using the root sampling method, and then used    
 to compute s(alpha,beta). the coherent elastic scattering        
 cross section was computed using the known lattice               
 structure and the debye-waller integrals from the lattice        
 dynamics model.                                                  
 1. j.u.koppel and d.h.houston, reference manual for endf thermal 
    neutron scattering data, general atomic report ga-8774        
    revised and reissued as endf-269 by the national nuclear      
    data center, july 1978.                                       
 2. j.a.young, n.f.wilkner, and d.e.parks, nukleonik              
    band 1, 295(1965).                                            
 3. j.a.young and j.u.koppel, j.chem.phys. 42, 357(1965).         
 4. r.e.macfarlane, new thermal neutron scattering files for      
    endf/b-vi release 2, los alamos national laboratory report    
    LA-12639-MS (ENDF-356) March 1994.