#P HF/6-31G(d) freq=HPModes

HF/6-31G(d) freq acetylene

0 1
X1
X2  1  1.0
C3  2  r3  1  90.0
C4  2  r3  1  90.0  3  180.0
H5  2  r5  1  90.0  4  180.0
H6  2  r5  1  90.0  3  180.0

r3=0.592723
r5=1.649676