Butadiene, equilibrium bond length

By combining high-level ab initio calculations with high-resolution infrared spectroscopy, the equilibrium bond lengths in x-frans-butadiene have been determined to an unprecedented precision of 0.1 pm. The values found for the pair of n-electron delocalized double bonds and the delocalized central single bond are 133.8 and 135.4 pm, respectively. The data provide definitive structural evidence that validates the fundamental concepts of n-electron delocalization, conjugation, and bond alternation in organic chemistry. 

Using a program that carries out molecular mechanics, find the equilibrium conformation of trans-1,3-butadiene. Compare the bond angles and bond lengths with those obtained with AMI or PM3 semiempirical methods. 

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