*HEADING
Verification of AC2D8 by cavity frequency calculation   
*NODE
  1,0
  5,0    ,0.1120
 41,0.113,0
 45,0.113,0.1120
 61,0.123,0
 65,0.123,0.1120
101,0.236,0.
105,0.236,0.1120
*NGEN,NSET=BOTTOM
  1, 41,10
 41, 61,10
 61,101,10
*NGEN,NSET=TOP
  5, 45,10
 45, 65,10
 65,105,10
*NFILL
BOTTOM,TOP,4
*ELEMENT,TYPE=AC2D8
 1,  1, 21, 23,  3, 11, 22, 13,  2
*ELGEN,ELSET=ALL
 1,2,2,1,2,20,2
 3,2,40,4
 7,2,20,2
 2,5,20,2
*MATERIAL,NAME=ALL
*DENSITY
 1.,
*ACOUSTIC MEDIUM,BULK MODULUS
1.183E5, 
*SOLID SECTION,MATERIAL=ALL,ELSET=ALL
 1,
*STEP
*FREQUENCY, eigensolver=lanczos, SIM=NO
 10, , ,-10.
*MODAL FILE
*END STEP