Table 20.

Threonine Dipeptide, Energy of the Conformers, RMS Deviations in ϕ, ψ, χ₁, χ₂ from the Ab Initio Data.

Conformer	Ab Initio a	PFF	OPLS-AA/L 1b	OPLS-AA/L 2b
1	0.00	0.77/4.3	−0.22/8.1	0.20/8.2
2	2.81	3.11/7.6	2.46/3.1	2.48/3.5
3	3.72	3.20/13.9	2.05/2.7	2.00/3.3
4	5.25	6.14/8.5	6.64/11.5	6.26/11.5
5	5.45	5.88/8.9	5.69/4.0	5.82/4.2
6	5.99	5.11/7.6	6.03/6.4	5.49/6.1
7	7.52	6.61/8.9	8.10/7.7	8.60/8.7
RMS errorc	—	0.75/8.9	0.87/6.9	0.87/7.1

Energies in kcal/mol, angles in degrees.

^aLMP2 cc-pVTZ(-f)//HF6-31G**, ref. 1.

^bRef. 1.

^cPositions of the minima shifted uniformly to achieve the lowest RMS deviation from the ab initio results.