Английская Википедия:Hydridonitride

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In chemistry, a hydridonitride (nitridohydride, nitride hydride, or hydride nitride) is a chemical compound that contains hydride (Шаблон:Chem2) and nitride (Шаблон:Chem2) ions in a single phase. These inorganic compounds are distinct from inorganic amides and imides as the hydrogen does not share a bond with nitrogen, and contain a larger proportion of metals.Шаблон:Cn

Structure

The hydride ion H⁻ is stabilised by being surrounded by electropositive elements such as alkalis 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 (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 exothermicly.

The molten metal flux 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.

Properties

Some hydridonitride are sensitive to water vapour 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

Шаблон:Anchor One Lutetium hydride doped with nitrogen is claimed to be a room temperature superconductor at up to 21°C at a pressure of 1GPa, which is considerably lower than for other polyhydrides. 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 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

name	formula	system	space group	unit cell (lengths in Å, volume in Å3)	structure	comment	optical	reference
lithium nitride hydride lithium hydridonitride	Li4NH	tetragonal	I41/a	a = 4.9865, c = 9.877, V = 234.9, Z = 4			yellow
calcium hydridonitride	Ca2NH	cubic	Fd3m	a = 10.13, Z = 16			brown-black
tricalcium silicon trinitride hydride	Ca3SiN3H	monoclinic	C2/c	a = 5.236, b = 10.461, c = 16.389, β = 91.182°, Z = 8	SiN4 tetrahedra in chains, Ca6H octahedra
Titanium hydridonitride	TiN0.3H1.1
	Ti0.7V0.3N0.23H0.8
	Ca3CrN3H	hexagonal	P63/m	a= 7.22772 c=5.06172 Z=2 V=228.998
hexacalcium dichromium hexanitride hydride	Ca6Cr2N6H		RШаблон:Overbar	a = 9.0042, c = 9.1898, Z = 3	planar CrN36−, CrN35−, octahedral Ca6H11+
strontium hydridonitride	Sr2NH		RШаблон:Overbarm	a = 3.870, c = 18.958			orange-yellow or black
Lithium distrontium dihydride nitride	LiSr2H2N	orthorhombic	Pnma	a = 7.4714, b = 3.7028, c = 13.2986, Z = 4	[SrH5N2]9−, [SrH4N3]11−, [LiH3N]5−
	Ti0.6Nb0.4N0.4H1.1
zirconium hydridonitride	ZrN0.17H1.65
	Ti0.88Zr0.12N0.28H1.39
	Zr0.7Nb0.3N0.33H1.15
barium hydridonitride	Ba2NH	hexagonal	RШаблон:Overbarm	a = 4.0262, c = 20.469		pure H− conductor
Tribarium chromium trinitride hydride	Ba3CrN3H	hexagonal	P63/m	a = 8.0270, c = 5.6240, Z = 2 V=313.83	planar CrN35–, octahedral HBa611+	nonmagnetic insulator	green
Lithium dieuropium nitride trihydride	LiEu2NH3	orthorhombic	Pnma	a = 7.4213, b = 3.6726, c = 13.1281, Z = 4	[Eu3+H7N2]10– and [Eu2+H6N3]13–		ruby red
Lutetium hydride nitride	LuH3-xNy		FmШаблон:Overbarm			< 1GPa	blue
Lutetium hydride nitride	LuH3-xNy		Immm			super conductor at 1GPa and 21°C	pink
Hafnium hydridonitride	HfNH0.6	hcp		a = 3.241, c = 5.198
Hafnium hydridonitride	HfNH	hcp		a = 3.216, c = 5.259
Thorium nitride hydride	ThNH2	fcc		a = 5.596