List of Figures

1. Flow chart of the JOYCE3.0 program.
2. UA model of the n-butane molecule. The number of interaction sites is reduced to four, which are completely described by six natural internal coordinates.
3. 6 natural IC for n-butane molecule: three bond lengths (R$_{12}$, R$_{23}$ and R$_{34}$), two bond angles ( $\theta _{123}$ and $\theta _{123}$) and the torsional dihedral ( $\delta _{1234}$) are evidenced by red, orange and blue lines, respectively.
4. Torsional energy profile for the n-butane molecule.
5. Torsional energy profile and 1-4 internal distance as a function of torsional dihedral $\delta$ for the n-butane molecule.
6. Some soft IC characterizing the PMME-H molecule.