chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, a hydridonitride (nitridohydride, nitride hydride, or hydride nitride) is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

that contains both

hydride In chemistry, a hydride is formally the anion of hydrogen (H−), a hydrogen ion with two electrons. In modern usage, this is typically only used for ionic bonds, but it is sometimes (and has been more frequently in the past) applied to all che ...

() and

nitride In chemistry, a nitride is a chemical compound of nitrogen. Nitrides can be inorganic or organic, ionic or covalent. The nitride anion, N3−, is very elusive but compounds of nitride are numerous, although rarely naturally occurring. Some nitr ...

()

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s. These

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

s are distinct from inorganic

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...

s and

imide In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications ...

s as the hydrogen does not share a bond with nitrogen, and usually contain a larger proportion of metals.

Structure

The hydride ion is stabilised by being surrounded by electropositive elements such as

alkali In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The a ...

s or alkaline earths. Quaternary compounds exist where nitrogen forms a complex with bonds to a transition or main group element. The hydride requires the presence of another alkaline earth element.

Production

Hydridonitrides may be produced by a process called

self-propagating high-temperature synthesis Self-propagating high-temperature synthesis (SHS) is a method for producing both inorganic and organic compounds by exothermic combustion reactions in solids of different nature. Reactions can occur between a solid reactant coupled with either a ga ...

(SHS) where a metal nitride is ignited in a hydrogen atmosphere. A metal (Ti, Zr, Hf, Y) can also be ignited in an atmosphere mixing hydrogen and nitrogen, and a hydridonitride is formed exothermically. The molten metal

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

technique involves dissolving metal nitrides and hydrides in an excess of molten alkaline earth metal, by heating till everything is molten, and then cooling until crystals form, but the metal is still liquid. Draining the liquid metal (and centrifuging) leaves the crystals of hydridonitride behind. A eutectic molten metal allows it to be cooled more. If liquid alkali metal is used as a flux to grow a hydridonitride crystal, excess metal can be removed using

liquid ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the formula . A stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pungent smell. It is widely used in fertilizers, ...

Properties

Some hydridonitrides are sensitive to

water vapour Water vapor, water vapour, or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor ...

in air. For non-stoichimetric compounds, as the proportion of hydrogen increases, the unit cell dimensions also increase, so hydrogen is not merely filling holes. When heated to a sufficiently high temperature, hydridonitrides lose hydrogen first to form a metallic nitride or alloy.

Room temperature superconductor

One lutetium hydride doped with nitrogen is claimed to be a room-temperature superconductor at up to 21°C at a pressure of 1

GPa Grading in education is the application of standardized measurements to evaluate different levels of student achievement in a course. Grades can be expressed as letters (usually A to F), as a range (for example, 1 to 6), percentages, or as num ...

, which is considerably lower than for other

polyhydride A polyhydride or superhydride is a compound that contains an abnormally large amount of hydrogen. This can be described as high hydrogen stoichiometry. Examples include iron pentahydride , , and . By contrast, the more well known lithium hydride o ...

s. This has been called "red matter" as it is red under high pressure, but blue at ambient conditions. The claim has been met with some skepticism as it was made by the same team that made similar claims retracted by ''Nature'' in 2022, claimed observation of solid metallic hydrogen in 2016 as well as other allegations. First attempts to replicate the results have failed.

Ashcroft Ashcroft may refer to: Places * Ashcroft, British Columbia, a village in Canada **Ashcroft House in Bagpath, Gloucestershire, England—eponym of the Canadian village * Ashcroft, New South Wales, a suburb of Sydney, Australia * Ashcroft, Colorado, ...

suggested metallic hydrogen could superconduct in 1968 at great pressures and in 2004 similarly that dense group IVa hydrides (as the new material) could also be superconductors at more accessible pressures.

List

References

{{Nitrides Nitrides Hydrides Mixed anion compounds