When using gaussian software for opt calculations, how do I fix the central position of the molecule (where there are no atoms, such as ethane), or limit the molecule to a local region of optimization?

I have used gic method in gaussian 16(https://gaussian.com/gic/) but failed to fix the central position.

# opt b3lyp/6-31g(d,p) geom=gic

Title Card Required

0 1

C 0 -3.11616551 -0.10136404 -0.07747210

H 0 -3.52940963 0.35783346 0.79617940

H 0 -3.52940963 0.35783346 -0.95112360

H 0 -3.35232462 -1.14497742 -0.07747210

C 0 -1.58674718 0.07885679 -0.07747210

H 0 -1.17350277 -0.38034307 -0.95112223

H 0 -1.35058858 1.12247028 -0.07747446

H 0 -1.17350280 -0.38033854 0.79618043

C -1 1.08660750 1.69629127 0.10644723

H -1 1.44328034 2.20068946 0.98009873

H -1 1.44328034 2.20068946 -0.76720427

H -1 0.01660750 1.69630446 0.10644723

C -1 1.59992321 0.24435912 0.10644723

H -1 1.24325240 -0.26003835 0.98009998

H -1 1.24324834 -0.26003979 -0.76720303

H -1 2.66992321 0.24434593 0.10644474

XC1(freeze)=XCntr(9,13)

YC1(freeze)=YCntr(9,13)

ZC1(freeze)=ZCntr(9,13)