dihedral angles scan get only for a free rotations between atoms

Jyothi, Thank you for your answer.

Yes that is correct, besides, groups (other atoms) that attached to the rotated atoms follow the rotation. My molecule is, lets say 1-2-3. I want to simultaneously rotate 1 and 3 at the same direction, means the rotation angle of 1-2 is negative value of 2-3.

I am kind of thinking whether there is a code to describe two dihedral angle rotation with opposite value in one line.

The scan coordinate can be varied independently. In GuassView you can simply change the step size and angle of your choice.

Even in D1 D2 S Z A mode, total number of calculations will be (Z+1)^2. As for the opposite value, if you are doing a full circle scan, -A would simply be A+ 360-2A. I mean, -60 degree is equivalent to +300 degree.

you can change sign

run this example

# opt=modredundant am1

Title Card Required

0 1

C -2.25773191 -0.07216495 0.00000000

C -0.86257191 -0.07216495 0.00000000

C -0.16503391 1.13558605 0.00000000

C -0.86268791 2.34409505 -0.00119900

C -2.25751291 2.34401705 -0.00167800

C -2.95511391 1.13581105 -0.00068200

H -2.80749091 -1.02448195 0.00045000

H -0.31306391 -1.02467795 0.00131500

H -0.31248791 3.29623805 -0.00125800

H -2.80763491 3.29629805 -0.00263100

H -4.05471791 1.13599405 -0.00086200

C 1.37496583 1.13569809 0.00088786

C 2.07239948 2.34402657 0.00088761

C 2.07255890 -0.07215588 0.00180346

C 3.46711148 2.34440563 0.00112091

H 1.52213795 3.29610418 -0.00061159

C 3.46769628 -0.07194961 0.00303285

H 1.52303070 -1.02459893 0.00198369

C 4.16503011 1.13604969 0.00255361

H 4.01690552 3.29678298 0.00048672

H 4.01745002 -1.02444306 0.00417000

C 5.70502988 1.13681835 0.00289380

C 6.40315402 -0.07111048 0.00432610

C 6.40193279 2.34507037 0.00165888

C 7.79786575 -0.07069152 0.00520519

H 5.85343587 -1.02350151 0.00607669

C 7.79707061 2.34566164 0.00154210

H 5.85186048 3.29719839 0.00035003

C 8.49509435 1.13806228 0.00345306

H 8.34820351 -1.02275336 0.00696815

H 8.34628042 3.29846848 0.00015285

H 9.59477427 1.13814256 0.00408740

D 4 3 12 13 S 6 60.000000

D 15 19 22 24 S 6 -60.000000