Timeline for Why rutile structure have primitive unit cell instead of body centered?
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 22, 2020 at 15:21 | comment | added | Mathew Mahindaratne | Not correct. Those 8 magnesium have same environment in next unit cell. | |
| May 22, 2020 at 10:45 | comment | added | Juila | Continuing from my last comment, I had a guess that the Mg at the centre of the unit cell actually has a different direction of polyhedra (formed with 6 hydrogen) compared to other 8 Mg ions at the corner, thus it is not contained in the same unit cell. Is my supposition correct? | |
| May 22, 2020 at 10:22 | comment | added | Juila | Yes, I do totally agree with you and see your logic. I see that the only possibility to define the arrangement is rutile type and that MgH3 (i.e. face centered unit cell) is not possible. However, what I am not clear now is why rutile is primitive (simple) unit cell instead of body centered, given that in the unit, we definitely do find another Mg atom (making 2 Mg per unit cell) whereas by definition, primitive unit cell should only have one Mg. I am not sure if my question is clear enough. And also, thank you very much. | |
| May 22, 2020 at 8:28 | comment | added | Mathew Mahindaratne | AS authors have noted, there is one and only one way to explain the arrangement of ions in crystal structure, which is rutile type. As I show you, six $\ce{H}$ arrange around one $\ce{Mg}$ such that it could have gotten for unit cell. But, if it is the unit cell, each $\ce{H}$ shares with two unit cells and one $\ce{Mg}$ shares with one cell. Thus, each unit cell contains $\ce{MgH3}$, which is impossible. Do you see my logic? | |
| May 22, 2020 at 8:06 | comment | added | Juila | Thank you very much for your kind and detailed answer! I just have one final ambiguity about the rutile structure. I understood that there are 2 MgH2 molecules in the unit cell and one short H-H bond in MgH2, which are all characteristic of rutile structure. However, then, by looking at the structure, can we not say any rutile structure is body centered instead of primitive? Really, from the structure, I am not convinced how rutile structure is then primitvie. Again, thanks a lot for your help. | |
| May 22, 2020 at 6:21 | history | answered | Mathew Mahindaratne | CC BY-SA 4.0 |