Theoretical Study of Weak Chemical Interactions in Solid Formamide

Structure and stability of solid formamide are studied theoretically at density-functional level in order to reveal the importance of hydrogen bonds and dispersion forces for intermolecular binding. The PBE-D2 and PBE-D3 functionals which include recent implementations of empirical dispersion corrections describe the crystal structure in good agreement with experimental results, whereas standard PBE fails. From wavefunction analyses and by decomposition of the total sublimation energy we find that weak CH⋯O hydrogen bonds exist between neighboring sheets of formamide molecules. Accordingly, we conclude that the formamide crystal consists of an extended three-dimensional hydrogen bond network.