Mixed-anion compounds

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Mixed-anion compounds, heteroanionic materials or mixed-anion materials are

anion. The compounds contain a single phase, rather than just a mixture.[1][2]

Use in materials science

By having more than one anion, many more compounds can be made, and properties tuned to desirable values.[3] In terms of optics, properties include

non-linearity.[5]
Mechanical properties can include ability to grow a large crystal, ability to form a thin layer, strength, or brittleness.

Thermal properties can include

thermal expansion coefficient
.

For electrical properties, electric conductivity,

charge-density wave
transition can be adjusted.

Production

Many of the non-metals that could make mixed-anion compounds may have greatly varying volatilities. This makes it more difficult to combine the elements together. Compounds may be produced in a solid state reaction, by heating solids together, either in a vacuum or a gas. Common gases used include, oxygen, hydrogen, ammonia, chlorine, fluorine, hydrogen sulfide, or carbon disulfide.

Soft chemical approaches to manufacture include solvothermal synthesis, or substituting atoms in a structure by others, including by water, oxygen, fluorine, or nitrogen. Teflon pouches can be used to separate different formulations. Thin film deposits can yield strained layers. High pressures can be used to prevent evaporation of volatiles. High pressure can result in different crystal forms, perhaps with higher coordination number.[1]

Kinds

Elemental
H
B BH B
C
CH
 CB C
N
NH
 NB NC N
O OH OB OC ON O
F
FH
 FB FC
FN
 FO F
Si SiH SiB SiC SiN SiO SiF Si
P PH PB PC PN
PO
 PF PSi P
S SH SB SC SN SO SF SSi SP S
Cl ClH ClB ClC
ClN
 ClO ClF ClSi
ClP
 ClS Cl
Ge GeH GeB GeC GeN GeO GeF GeSi GeP GeS GeCl Ge
As AsH AsB AsC AsN
AsO
 AsF AsSi AsP AsS AsCl AsGe As
Se
SeH
 SeB SeC SeN
SeO
 SeF SeSi SeP
SeS
 SeCl SeGe SeAs Se
Br BrH BrB
BrC
 BrN BrO BrF BrSi
BrP
 BrS BrCl BrGe
BrAs
 BrSe Br
Sb SbH SbB SbC SbN SbO SbF SbSi SbP SbS SbCl SbGe SbAs SbSe SbBr Sb
Te
TeH
 TeB TeC TeN TeO TeF TeSi TeP TeS TeCl TeGe
TeAs
 TeSe TeBr TeSb Te
I IH IB
IC
IN
 IO IF ISi
IP
 IS ICl IGe
IAs
 ISe IBr ISb
ITe
 I
Bi BiH BiB BiC BiN
BiO
 BiF BiSi BiP BiS BiCl BiGe BiAs BiSe BiBr BiSb BiTe BiI

Molecular anions

Oxyanions

Fluoroanions

Mixed valency and oligomers

Some elements can form several kinds of anions, and compounds may exist with more than one. Examples include the iodate periodates,[10] sulfite sulfates, selenate selenites, tellurite tellurates, nitrate nitrites, phosphate phosphites, and arsenate arsenites.

These kinds also include different oligomeric forms such as phosphates or fluorotitanates, such as [Ti4F20]4- and [TiF5]−.[11]

Organic

References

  1. ^
    PMID 29472526
    .
  2. ISBN 978-1839165122
    .
  3. doi:10.5940/jcrsj.60.240
    .
  4. S2CID 244141502
    .
  5. S2CID 197213596
    .
  6. ^
    doi:10.1016/j.ccr.2017.06.010
    .
  7. PMID 23831607
    .
  8. doi:10.1002/ejic.201000119
    .
  9. S2CID 216073355
    .
  10. S2CID 245278633
    .
  11. S2CID 104344701
    .
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