Potential energy states

This particular sequence of conformations-trans bonds that advance the helix along the axis, alternating with gauche bonds which provide the twist-takes the chain through a series of relatively low potential energy states and generates a structure with minimum steric hindrance between substituents. If the polymer series is extended to include bulkier substituents, for example. 

In addition to being additive, intermolecular forces can also be competitive. More specifically, the orientation of the molecules that is optimal to satisfy one type of interaction may not be ideal for another type. The result is a compromise amongst the individual attractive forces to achieve the lowest potential energy state for the crystal. Furthermore, AHm is not the energy required to completely eliminate intermolecular attraction at Tm but the energy required to reduce the attraction to its level in the liquid that level being a function of intermolecular distance. 

Knowledge of the potential energy curve as a function of position lets us predict the net force on the object at each position. From either side, the force is directed toward the bottom the force is always in the direction in which the slope of the potential energy curve is negative. From the definition of potential energy stated earlier, it can be shown that... 

We calculated the free energies of all the minima in order to determine the equilibrium probability distribution (see Section IV.C.2). We found that the several hundred lowest free energy minima have about the same free energy, and that no single minimum has an equilibrium occupation probability which exceeds 0.004. This is in stark contrast with unsolvated tetra-alanine, where the ground state had an equilibrium occupation probability of 0.748, and the lowest three potential energy states accounted for 0.936 of the total equilibrium probability. 

Use blocks, pins, or chains to restrain energy when equipment cannot be brought to a zero potential energy state. 

As r 0, the system is confined more closely to its minimum potential energy state, until at r = 0+, only the minimum energy state has a nonzero probability of being observed. 

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