Steric energy, molecular modelling

Figure 3. Three-dimensional modeling of cardiolipin tetralinoleoyl created by Chem3D Pro, ver 4.0 with running of MM2, a software of molecular mechanics, to minimize steric energy in vacuo. Each atom is displayed in colour, H (blue), C (black), O (red), and P (purple) (see separate colour tip).

Additionally, the s-trans conformation of t (and by analogy A) is believed to be the lower energy form molecular models, Hiickel calculations, and X-ray structure data support the conclusion that an unfavorable steric interaction exists between the methyl group and the carbon monoxide for the s-trans conformer2-35. 

Molecular Mechanics. Molecular mechanics (MM), or empirical force field methods (EFF), are so called because they are a model based on equations from Newtonian mechanics. This model assumes that atoms are hard spheres attached by networks of springs, with discrete force constants. The force constants in the equations are adjusted empirically to repro duce experimental observations. The net result is a model which relates the "mechanical" forces within a structure to its properties. Force fields are made up of sets of equations each of which represents an element of the decomposition of the total energy of a system (not a quantum mechanical eneigy, but a classical mechanical one). The sum of the components is called the force field eneigy, or steric energy, which also routinely includes the electrostatic eneigy components. Typically, the steric energy is expressed as... 

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