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Allotropy. Property of some chemical elements to exist in two or more different forms. Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure. Allotropy or allotropism (from Ancient Greek ἄλλος (allos) 'other' and τρόπος (tropos) 'manner, form') is the property of some ...
Phase information is based on the work of G. C. Vezzoli, et al., as reviewed by David Young; as Young notes, "The literature on the allotropy of sulfur presents the most complex and confused situation of all the elements." [8] [9] Phase information are limited to ≤50 kbar and thus omitting metallic phases. [10]
Elements including metals may exhibit polymorphism. Allotropy is the term used when describing elements having different forms and is used commonly in the field of metallurgy. Some (but not all) allotropes are also polymorphs. For example, iron has three allotropes that are also polymorphs. Alpha-iron, which exists at room temperature, has a ...
The K 4 crystal. The Laves graph or K 4 crystal is a theoretically predicted three-dimensional crystalline metastable carbon structure in which each carbon atom is bonded to three others, at 120° angles (like graphite), but where the bond planes of adjacent layers lie at an angle of 70.5°, rather than coinciding. [34] [35]
On rare occasions, P 4 O 7, P 4 O 8, and P 4 O 9 are also formed, but in small amounts. This combustion gives phosphorus(V) oxide, which consists of P 4 O 10 tetrahedral with oxygen inserted between the phosphorus atoms and at their vertices: P 4 + 5 O 2 → P 4 O 10. The odour of combustion of this form has a characteristic garlic smell.
The alpha iron (α-Fe) is a body-centered cubic (BCC) and the gamma iron (γ-Fe) is a face-centered cubic (FCC). At atmospheric pressure, three allotropic forms of iron exist, depending on temperature: alpha iron (α-Fe, ferrite), gamma iron (γ-Fe, austenite), and delta iron (δ-Fe). At very high pressure, a fourth form exists, epsilon iron ...
Transition temperature. In crystallography, the transition temperature is the temperature at which a material changes from one crystal state (allotrope) to another. [1] More formally, it is the temperature at which two crystalline forms of a substance can co-exist in equilibrium.
The common allotrope of elemental oxygen on Earth, O2, is generally known as oxygen, but may be called dioxygen, diatomic oxygen, molecular oxygen, dioxidene or oxygen gas to distinguish it from the element itself and from the triatomic allotrope ozone, O3. As a major component (about 21% by volume) of Earth's atmosphere, elemental oxygen is ...