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A molecular solid is a solid consisting of discrete molecules. The cohesive forces that bind the molecules together are van der Waals forces , dipole–dipole interactions , quadrupole interactions , π–π interactions , hydrogen bonding , halogen bonding , London dispersion forces , and in some molecular solids, coulombic interactions .
As this example shows, there can be no sharp boundary between molecular and network covalent solids. Intermediate kinds of bonding: A solid with extensive hydrogen bonding will be considered a molecular solid, yet strong hydrogen bonds can have a significant degree of covalent character. As noted above, covalent and ionic bonds form a continuum ...
A plastic crystal is a molecular solid with long-range positional order but with constituent molecules retaining rotational freedom; in an orientational glass this degree of freedom is frozen in a quenched disordered state. Similarly, in a spin glass magnetic disorder is frozen.
Mesomorphic states: States of matter intermediate between solid and liquid. Plastic crystal: A molecular solid with long-range positional order but with constituent molecules retaining rotational freedom. Liquid crystal: Properties intermediate between liquids and crystals. Generally, able to flow like a liquid but exhibiting long-range ...
Crystalline solids and molecular solids are two opposite extreme cases of materials that exhibit substantially different transport mechanisms. While in atomic solids transport is intra-molecular, also known as band transport, in molecular solids the transport is inter-molecular, also known as hopping transport.
It follows that, in molecular solids, the heat capacity per mole of molecules will usually be close to 3nR, where n is the number of atoms per molecule. Thus n atoms of a solid should in principle store twice as much energy as n atoms of a monatomic gas. One way to look at this result is to observe that the monatomic gas can only store energy ...
A molecular vibration is a periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. The typical vibrational frequencies range from less than 10 13 Hz to approximately 10 14 Hz, corresponding to wavenumbers of approximately 300 to 3000 cm −1 and wavelengths of approximately 30 to 3 μm.
The interest stems from that accurate measurements of the unit cell volume, atomic weight and mass density of a pure crystalline solid provide a direct determination of the Avogadro constant. [3] The CODATA recommended value for the molar volume of silicon is 1.205 883 199 (60) × 10 −5 m 3 ⋅mol −1, with a relative standard uncertainty of ...