# Oxybismuthides

Oxybismuthides or bismuthide oxides are chemical compounds formally containing the group BiO, with one bismuth and one oxygen atom. The bismuth and oxygen are not bound together as in bismuthates, instead they make a separate presence bound to the cations (metals), and could be considered as a mixed bismuthide-oxide compound. So a compound with O$_m$Bi$_n$ requires cations to balance a negative charge of 2m+3n. The cations will have charges of +2 or +3. The trications are often rare earth elements or actinides. They are in the category of oxypnictide compounds.
Many of the bismuthide oxides have bismuth in an unusual -2 oxidation state. The ones with Ln$_2$BiO$_2$ have the anti-ThCr$_2$Si$_2$ structure. They include alternating layers of LnO (anti-fluorite-type) and LnBiO. The Eu$_4$Bi$_2$O has an anti-K$_2$NiF$_4$ structure, the same as for Na$_2$Ti$_2$As$_2$O. Some other compounds contain calcium and a rare earth CaRE$_3$BiO$_4$, and Ca$_2$RE$_8$Bi$_3$O$_{10}$.
Some of these compounds are superconductors at very low temperatures and many are semiconductors at standard conditions.

## Examples

| formula | name | mw | structure | space group | cell | appearance | properties | supercondicting T$_c$ |
| Ti$_8$BiO$_7$ | octatitanium bismuthide heptoxide | | orthorhombic | Cmmm | I = 7.8473 Å, b = 16.829 Å, c = 3.0256 Å | silver | conductor | |
| (SrF)$_2$Ti$_2$Bi$_2$O | | | tetragonal | I4/mmm | | | | |
| BaTi$_2$Bi$_2$O | | | tetragonal | | a = 4.046 Å, c = 7.272 Å | | | |
| LaNiBiO | Lanthanum nickel oxybismuthide | | | | | | | 4.2 |
| Ce$_2$O$_2$Bi | | | tetragonal | I4/mmm | a=4.034 c=13.736 | | | |
| Nd$_2$BiO$_2$ | | 529.46 | tetragonal | I4/mmm | a=399.11 c = 1366.3 V=217.53 | dark grey | | |
| Tb$_2$BiO$_2$ | | 558.82 | tetragonal | I4/mmm | a=389.62 c=1331.7 V=202.16 | dark grey | | |
| Dy$_2$BiO$_2$ | | 565.98 | tetragonal | I4/mmm | a=387.61 c=1323.3 V=198.82 | dark grey | | |
| Ho$_2$BiO$_2$ | | 570.84 | tetragonal | I4/mmm | a=385.83 c=1321.8 V=196.77 | dark grey | | |
| La$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=4.08083 c=13.9866 V=198.74 | | | |
| Er$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=3.84531 c=13.1513 V=194.48 | | | |
| (EuF)$_2$Ti$_2$Bi$_2$O | | | tetragonal | I4/mmm | a=4.1172 c=21.2718 | | | |
| Gd$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=3.9181 c=13.4246 V=206.09 | | | |
| Y$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=3.8734 c=13.2469 V=198.74 | | | |
| Pr$_2$BiO$_2$ | | | tetragonal | I4/mmm | | | | |
| Nd$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=3.99258 c=13.6663 V=217.851 | | | |
| Ho$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=3.86212 c=13.2262 V=197.28 | | | |
| Sm$_2$BiO$_2$ | | | tetragonal | I4/mmm | a=3.95296 c=13.5083 V=211.074 | | | |
| Sm$_4$Bi$_2$O | | | | | | | | |
| Eu$_4$Bi$_2$O | | | | | | | | |
| Ba$_2$Cd2.13Bi$_3$O | Dibarium tricadmium bismuthide(-I,-III) oxide | | tetragonal | I4/mmm | a = 4.7396 c = 43.601 V=979.5 Z=4 | black | | |
| Gd$_3$BiO$_3$ | | | monoclinic | C2/m | | | | |
| Gd$_8$Bi$_3$O$_8$ | | | monoclinic | C2/m | | grey | | |
| Ca$_2$RE$_7$Bi$_5$O$_5$ | | | | | | grey | | |
| Cm$_2$BiO$_2$ | | | tetragonal | I4/mmmm | a=3.957 c=13.359 | | | |
| Am$_2$BiO$_2$ | Americium dioxybismuthide | | orthorhombic | Pnam | a=5.053 b=8.092 c=5.738 | | | |