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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 .
The study of molecules by molecular physics and theoretical chemistry is largely based on quantum mechanics and is essential for the understanding of the chemical bond. The simplest of molecules is the hydrogen molecule-ion, H 2 +, and the simplest of all the chemical bonds is the one-electron bond.
Quantum dots have properties intermediate between bulk semiconductors and discrete atoms or molecules. Their optoelectronic properties change as a function of both size and shape. [6] [7] Larger QDs of 5–6 nm diameter emit longer wavelengths, with colors such as orange, or red. Smaller QDs (2–3 nm) emit shorter wavelengths, yielding colors ...
When covalent bonds link long chains of atoms in large molecules, however (as in polymers such as nylon), or when covalent bonds extend in networks through solids that are not composed of discrete molecules (such as diamond or quartz or the silicate minerals in many types of rock) then the structures that result may be both strong and tough, at ...
There are four formula units (in this case, discrete molecules) per unit cell, giving a density of 5.09 g·cm −3. [25] The OsF 6 molecule itself (the form important for the liquid or gas phase) has octahedral molecular geometry, which has point group (O h). The Os–F bond length is 1.827 Å. [25] Partial hydrolysis of OsF 6 produces OsOF 4. [26]
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
The example given, paraffin wax, is a member of a family of hydrocarbon molecules of differing chain lengths, with high-density polyethylene at the long-chain end of the series. High-density polyethylene can be a strong material: when the hydrocarbon chains are well aligned, the resulting fibers rival the strength of steel.
Molecular dynamics (MD) is a computer simulation method for analyzing the physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a fixed period of time, giving a view of the dynamic "evolution" of the system.