Structural and electronic properties of L-amino acids

The structural and electronic properties of four L-amino acids alanine, leucine, isoleucine, and valine have\udbeen investigated using density functional theory sDFTd and the generalized gradient approximation. Within\udthe crystals, it is found that the constituent molecules adopt zwitterionic configurations, in agreement with\udexperimental work. Lattice constants are found to be in good agreement with experimentally determined\udvalues, although certain discrepancies do exist due to the description of van derWaals interactions.We find that\udthese materials possess wide DFT band gaps in the region of 5 eV, with electrons highly localized to the\udconstituent molecules. It is found that the main mechanisms behind crystal formation are dipolar interactions\udand hydrogen bonding of a primarily electrostatic character, in agreement with current biochemical understanding\udof these systems. The electronic structure suggests that the amine and carboxy functional groups are\uddominant in determining band structure