*HEADING
 EIGENVALUE ANALYSIS OF AN UNCONSTRAINED 1-ELEMENT MESH  [COH2D4]
*NODE,NSET=ALL
 1, 0., 0.
 2, 10., 0.
 3, 10., 10.
 4, 0., 10.
*ELEMENT,TYPE=COH2D4,ELSET=EALL
 1, 1, 2, 3, 4
*COHESIVE SECTION, MATERIAL=COH, ELSET=EALL, RESPONSE=TRACTION SEPARATION, THICKNESS=GEOMETRY
*MATERIAL,NAME=COH
*ELASTIC, TYPE=TRACTION
  2.0E11, 1.0E11, 1.0E11
*DENSITY
 7800., 
*STEP
*FREQUENCY, EIGENSOLVER=LANCZOS
8, , ,-1.E6 
*END STEP