Origins of hydration differences in homochiral and racemic crystals of aspartic acid.

The propensity for crystalline hydrates of organic molecules to form is related to the strength of the interactions between molecules, including the chiral composition of the molecular solids. Specifically, homochiral versus racemic crystalline samples can exhibit distinct differences in their ability to form energetically stable hydrates. The focus of the current study is a comparison of the crystal structures and intermolecular forces found in solid-state L-aspartic acid, DL-aspartic acid, and L-aspartic acid monohydrate.

London force correction disparity in the modeling of crystalline asparagine and glutamine.

Solid-state density functional theory is a powerful computational method used to provide insight into the low-frequency vibrations of crystalline solids. A known limitation of this method is its general underestimation of weak intermolecular forces. Semiempirical London force corrections have been developed to augment density functional theory calculations with the ultimate goal being corrections that are applicable to a range of compounds.

Terahertz vibrations of crystalline acyclic and cyclic diglycine: benchmarks for London force correction models.

Terahertz spectroscopy provides direct information concerning weak intermolecular forces in crystalline molecular solids and therefore acts as an excellent method for calibrating and evaluating computational models for noncovalent interactions. In this study, the low-frequency vibrations of two dipeptides were compared, acyclic diglycine and cyclic diglycine, as benchmark systems for gauging the performance of semiempirical London force correction approaches. The diglycine samples were investigated using pulsed terahertz spectroscopy from 10 to 100 cm(-1) and then analyzed using solid-state density functional theory (DFT) augmented with existing London force corrections, as well as a new parametrization (DFT-DX) based on known experimental values.