Simple cubic structure relative structural stability

HOMO). A similar approach can stabilize the rocksalt structure (the AB analog of the elemental simple cubic structure above). By introducing a large electronegativity difference between A and B, we generate a substantial HOMO-LUMO (lowest unoccupied molecular orbital) gap. Based on the relative positions of A and B s and p valence levels, a number of different sequences of structural energies can be expected. Only for the case in which both s and p orbitals of A lie below those of B will the rocksalt structure be favored. 

The fact that the folding (and unfolding) kinetics of relatively small, two-state proteins can be predicted with reasonable accuracy from global features of the native state like the contact order, stability, and number of contacts supports the idea that the details of protein structure are not required to capture the key features of protein folding, so that reduced representations should be adequate. However, the most widely used simple heteropolymer models, those restricted to a simple cubic lattice, predict that stability is more important than native structure, in contrast to the experimental data for proteins. In this section we seek to understand why lattice models differ from proteins in this regard. Doing so is of importance because complete details of the folding trajectories of such models... 

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