Molecular Crystals

Molecular Crystals

 

crystals formed by molecules bonded by weak van der Waals’ forces or by a hydrogen bond. A stronger covalent bond acts between the atoms within molecules. The phase transformations of molecular crystals—melting, sublimation, and polymorphic transitions—usually take place without the destruction of individual molecules.

Most molecular crystals are crystals of organic compounds. Naphthalene is a typical molecular crystal. Molecular crystals are also formed by certain simple substances (H2, the halogens, N2, O2, and S8), binary compounds such as H2O, CO2, N2O4, organometallic compounds, and certain complex compounds. The crystals of polymers, and also of proteins and nucleic acids, are also molecular crystals. Crystals of solidified inert gases, in which van der Waals’ forces bond atoms rather than molecules, are a special case of molecular crystals.

Low melting points, high coefficients of thermal expansion, high compressibility, and low hardness are characteristic of typical molecular crystals. Under ordinary conditions most molecular crystals are dielectrics. Some molecular crystals, such as the organic dyes, are semiconductors.

REFERENCES

Kitaigorodskii, A. I. Molekuliarnye kristally. Moscow, 1971.
Bokii, G. B. Kristallokhimiia. Moscow, 1971.

P. M. ZORKII

References in periodicals archive ?
Bondi, Physical properties of molecular crystals, liquids, and glasses, Wiley, New York, (1968).
Containing Tetrabutyl-Ammonium Tetraphenyl-Boride," Molecular Crystals and Liquid Crystals, vol.
Manaila-Maximean, "New aspect of the voltage/confinement ratio phase diagram for a confined homeotropic cholesteric," Molecular Crystals and Liquid Crystals, vol.
Makoto Moriya of Shizuoka University in Japan investigated molecular crystals for this purpose.
I aim to develop new BC materials by exploiting phase transitions in non-magnetic solids whose structural and thermal properties are strongly coupled, namely ferroelectric salts, molecular crystals and hybrid materials.
Bertelson, "Reminiscences about organic photochromics," Molecular Crystals and Liquid Crystals Science and Technology A: Molecular Crystals and Liquid Crystals, vol.
Docherty, "Polymorphism in molecular crystals: stabilization of a metastable form by conformational mimicry," Journal of the American Chemical Society, vol.
Among their topics are computer simulations of charged colloids, layer-by-layer assembly on stimuli-responsive microgels, the dynamics and structure of water nanotube clusters confined to nanoporous molecular crystals, the quantum electrochemical study of benzene derivatives, possibilities and limitations of electrokinetic methods in biological interfaces, and surface characteristics and attachment behaviors of bacterial cells.
The first four chapters examine the interplay of charge (polarons) and neutral (excitons) photoexcitations in pi-conjugated polymers, oligomers, and molecular crystals in the time domain of 100 fs-2 ns.
Crystals of purines are formed by molecules and classified as molecular crystals (15).
In organic molecular crystals, hydrogen bonds often constitute the strongest intermolecular synthon [21], and hence often dictate the preferred packing arrangement of the molecules.
The experiments were in the fields of superconductivity, molecular crystals, and molecular electronics and published in such respected journals as Science, Nature, and others.