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A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids.A type of quasiparticle in physics, [1] a phonon is an excited state in the quantum mechanical quantization of the modes of vibrations for elastic structures of interacting particles.
A chiral substance is enantiopure when only one of two possible enantiomers is present so that all molecules within a sample have the same chirality sense. Use of homochiral as a synonym is strongly discouraged. [22] A chiral substance is enantioenriched or heterochiral when its enantiomeric ratio is greater than 50:50 but less than 100:0. [23]
The term "chiral" in general is used to describe the object that is non-superposable on its mirror image. [18] In chemistry, chirality usually refers to molecules. Two mirror images of a chiral molecule are called enantiomers or optical isomers. Pairs of enantiomers are often designated as "right-", "left-handed" or, if they have no bias ...
A theory that is asymmetric with respect to chiralities is called a chiral theory, while a non-chiral (i.e., parity-symmetric) theory is sometimes called a vector theory. Many pieces of the Standard Model of physics are non-chiral, which is traceable to anomaly cancellation in chiral theories.
Chiral phosphine ligands, especially C 2-symmetric ligands, are the source of chirality in most asymmetric hydrogenation catalysts. Of these the BINAP ligand is well-known, as a result of its Nobel Prize-winning application in the Noyori asymmetric hydrogenation. [3] Chiral phosphine ligands can be generally classified as mono- or bidentate ...
Chiral inversion is the process of conversion of one enantiomer of a chiral molecule to its mirror-image version with no other change in the molecule. [1] [2] [3] [4]Chiral inversion happens depending on various factors (viz. biological-, solvent-, light-, temperature- induced, etc.) and the energy barrier energy barrier associated with the stereogenic element present in the chiral molecule. 2 ...
The term chiral / ˈ k aɪ r əl / describes an object, especially a molecule, which has or produces a non-superposable mirror image of itself. In chemistry, such a molecule is called an enantiomer or is said to exhibit chirality or enantiomerism.
These processes are called Umklapp scattering and change the total phonon momentum. Umklapp scattering is the dominant process for electrical resistivity at low temperatures for low defect crystals [1] (as opposed to phonon-electron scattering, which dominates at high temperatures, and high-defect lattices which lead to scattering at any ...