Use $ams2026

Calculate the torsional potential energy profile of biphenyl with DFTB.

Build biphenyl from SMILES c1ccccc1-c2ccccc2. Identify the central inter-ring
C-C bond and the four atoms defining the inter-ring dihedral by inspecting
the ChemicalSystem bonds.

Run a constrained AMS PES Scan over the inter-ring dihedral from 0 to 180
degrees in 10 degree steps. Use DFTB.

Plot relative energy in kcal/mol vs dihedral angle. In the report, identify
the minimum-energy twist angle and the torsional barriers to the planar and
perpendicular structures.

Include pictures of the optimized structures at the planar geometry, the
minimum-energy geometry, and the perpendicular geometry. Include a table
with dihedral angle, absolute energy, and relative energy for all scan points.