<blockquote>
  <p>Should one assume that the mineral petitjeanite and the chemical discussed in the recent Chemical &amp; Engineering News article Photocatalyst shreds drinking water contaminant PFOA are probably the same crystal configuration and unit cell, or can there be some variety?</p>
</blockquote>

<p>No you cannot assume the structure from the formula, many materials have polymorphs (think graphite vs. diamond). To know if the structures are the same you must look at the diffraction pattern from <a href="https://pubs.acs.org/doi/10.1021/acs.estlett.8b00395" rel="nofollow noreferrer">the paper</a>. In the paper the synthesized bismuth oxyhydroxyphosphate matches that of petitjeanite so in this case that is the prototype structure.</p>

<p><a href="https://pubs.acs.org/doi/10.1021/acs.estlett.8b00395" rel="nofollow noreferrer"><img src="https://i.sstatic.net/UqJAF.png" alt="enter image description here"></a></p>

<p>Using the information about diffraction, from the ICDD Databse (pdf 01-082-8058)we find that petitjeanite is a triclinic system of the <span class="math-container">$\mathrm P\bar 1$</span> space group (#2). with lattice parameters of: </p>

<p><span class="math-container">$\require{mediawiki-texvc}$</span>
<span class="math-container">$$a = 9.798\AA; ~ b =  7.250\AA; ~ c= 6.866 \AA; \qquad \alpha = 88.280^\circ \beta = 115.270^\circ ~ \gamma = 110.700^\circ$$</span></p>

<p>and atomic positions of:
<span class="math-container">$$\begin{array}{c|lll}
\text{Atom}&amp;x&amp;y&amp;z\\
\hline
\ce{Bi}&amp;~~~0.52327&amp;~~~0.41421&amp;~~~0.7523\\
\ce{Bi}&amp;~~~0.29838&amp;~~~0.74044&amp;~~~0.55549\\
\ce{Bi}&amp;~~~0.07735&amp;~~~0.1609&amp;~~~0.28045\\
\ce{P}&amp;~~~0.6952&amp;~~~0.0172&amp;~~~0.9215\\
\ce{P}&amp;~~~0.0961&amp;~~~0.372&amp;~~~0.7862\\
\ce{O}&amp;~~~0.3777&amp;~~~0.5382&amp;~~~0.4759\\
\ce{O}&amp;~~~0.3066&amp;~~~0.1549&amp;~~~0.5579\\
\ce{O}&amp;~~~0.859&amp;~~~0.0275&amp;~~~0.8943\\
\ce{O}&amp;~~~0.5569&amp;-0.2084&amp;~~~0.8602\\
\ce{O}&amp;~~~0.621&amp;~~~0.1596&amp;~~~0.7526\\
\ce{O}&amp;~~~0.7684&amp;~~~0.1052&amp;~~~1.1811\\
\ce{O}&amp;~~~0.2584&amp;~~~0.5101&amp;~~~0.7497\\
\ce{O}&amp;-0.0468&amp;~~~0.4637&amp;~~~0.6902\\
\ce{O}&amp;~~~0.0209&amp;~~~0.1498&amp;~~~0.6362\\
\ce{O}&amp;~~~0.1695&amp;~~~0.3727&amp;~~~1.0506\\
\end{array}
$$</span></p>

<p>and last but not least this renders to an image of:</p>

<p><a href="https://i.sstatic.net/fwn9n.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/fwn9n.png" alt="unit cell"></a></p>

<p>Purple: Bi<br>
Orange: P<br>
Red: O</p>

CC BY-SA 4.0
2019-04-13T16:13:21.040Z
2019-04-13T16:13:21.040Z
A.K.
<p>Having the same formula does not mean that the crystal structure is the same. An example is calcium carbonate, which can form the minerals calcite or aragonite. So you have to read the publications to know if they have done X-ray diffraction to positively identify the crystals as petitjeanite. If that is the case, then the crystal structure is triclinic and the relevant data can be found at <a href="http://webmineral.com/data/Petitjeanite.shtml#.XK0Vh_kzZaQ" rel="nofollow noreferrer">webmineral.com</a>.</p>

<p>ETA: Also note that the unit cell does not necessarily correspond to the visible crystal habit.</p>

CC BY-SA 4.0
2019-04-09T22:05:54.877Z
2019-04-09T22:05:54.877Z
haresfur
<p>The question in Chemistry SE <a href="https://chemistry.stackexchange.com/q/112398/16035">What is the crystal structure of bismuth oxyhydroxyphosphate (BOHP)?</a> is about a catalyst synthesized by accident. A link in <a href="https://chemistry.stackexchange.com/questions/112398/what-is-the-crystal-structure-of-bismuth-oxyhydroxyphosphate-bohp?noredirect=1#comment211511_112398">this comment</a> points to the page <a href="https://www.mindat.org/min-3329.html" rel="nofollow noreferrer">https://www.mindat.org/min-3329.html</a> which is for the mineral petitjeanite, or <span class="math-container">$\ce{Bi3(PO4)2O(OH)}$</span>. There are about 38 photos available there, and there seems to be quite a diverse range of appearances to my untrained eye.</p>

<p>I was wondering if a drawing or computer-generated image of a unit cell for petitjeanite would exist in any database or website for mineralogy and crystal structures, something like those shown in these questions <a href="https://chemistry.stackexchange.com/q/73755/16035">1</a>, <a href="https://chemistry.stackexchange.com/q/71564/16035">2</a>, <a href="https://chemistry.stackexchange.com/q/73254/16035">3</a>.</p>

<p>Should one assume that the mineral petitjeanite and the chemical discussed in the recent Chemical &amp; Engineering News article <a href="https://cen.acs.org/environment/persistent-pollutants/Photocatalyst-shreds-drinking-water-contaminant/96/i36" rel="nofollow noreferrer">Photocatalyst shreds drinking water contaminant PFOA</a> are probably the same crystal configuration and unit cell, or can there be some variety?</p>

<hr>

<p>The paper also includes this SEM image of microcrystals of the "inadvertently produced bismuth oxyhydroxyphosphate (BOHP)."</p>

<p><a href="https://i.sstatic.net/BV1sI.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/BV1sI.jpg" alt="enter image description here"></a></p>

<blockquote>
  <p>The accidentally synthesized BOHP (shown) can break down the toxic industrial contaminant PFOA faster than any other photocatalyst. Credit: Environ. Sci. Technol. Lett.</p>
</blockquote>

<mineralogy><crystals><crystallography>
What does the unit cell of petitjeanite look like?
uhoh
# What does the unit cell of petitjeanite look like?

(Asked by: username_0 on 2019-04-09)

The question in Chemistry SE [What is the crystal structure of bismuth oxyhydroxyphosphate (BOHP)?](https://chemistry.stackexchange.com/q/112398/16035) is about a catalyst synthesized by accident. A link in [this comment](https://chemistry.stackexchange.com/questions/112398/what-is-the-crystal-structure-of-bismuth-oxyhydroxyphosphate-bohp?noredirect=1#comment211511_112398) points to the page <https://www.mindat.org/min-3329.html> which is for the mineral petitjeanite, or $\ce{Bi3(PO4)2O(OH)}$. There are about 38 photos available there, and there seems to be quite a diverse range of appearances to my untrained eye.

I was wondering if a drawing or computer-generated image of a unit cell for petitjeanite would exist in any database or website for mineralogy and crystal structures, something like those shown in these questions [1](https://chemistry.stackexchange.com/q/73755/16035), [2](https://chemistry.stackexchange.com/q/71564/16035), [3](https://chemistry.stackexchange.com/q/73254/16035).

Should one assume that the mineral petitjeanite and the chemical discussed in the recent Chemical & Engineering News article [Photocatalyst shreds drinking water contaminant PFOA](https://cen.acs.org/environment/persistent-pollutants/Photocatalyst-shreds-drinking-water-contaminant/96/i36) are probably the same crystal configuration and unit cell, or can there be some variety?

---

The paper also includes this SEM image of microcrystals of the "inadvertently produced bismuth oxyhydroxyphosphate (BOHP)."

[![enter image description here](https://i.sstatic.net/BV1sI.jpg)](https://i.sstatic.net/BV1sI.jpg)

> The accidentally synthesized BOHP (shown) can break down the toxic industrial contaminant PFOA faster than any other photocatalyst. Credit: Environ. Sci. Technol. Lett.

**Tags:** mineralogy, crystals, crystallography


---

## 2 answers

### Answer by username_1 on 2019-04-13. Score: 3 | Accepted answer

> Should one assume that the mineral petitjeanite and the chemical discussed in the recent Chemical & Engineering News article Photocatalyst shreds drinking water contaminant PFOA are probably the same crystal configuration and unit cell, or can there be some variety?

No you cannot assume the structure from the formula, many materials have polymorphs (think graphite vs. diamond). To know if the structures are the same you must look at the diffraction pattern from [the paper](https://pubs.acs.org/doi/10.1021/acs.estlett.8b00395). In the paper the synthesized bismuth oxyhydroxyphosphate matches that of petitjeanite so in this case that is the prototype structure.

[![enter image description here](https://i.sstatic.net/UqJAF.png)](https://pubs.acs.org/doi/10.1021/acs.estlett.8b00395)

Using the information about diffraction, from the ICDD Databse (pdf 01-082-8058)we find that petitjeanite is a triclinic system of the $\mathrm P\bar 1$ space group (#2). with lattice parameters of:

$\require{mediawiki-texvc}$
$$a = 9.798\AA; ~ b = 7.250\AA; ~ c= 6.866 \AA; \qquad \alpha = 88.280^\circ \beta = 115.270^\circ ~ \gamma = 110.700^\circ$$

and atomic positions of:
$$\begin{array}{c|lll}
\text{Atom}&x&y&z\\
\hline
\ce{Bi}&~~~0.52327&~~~0.41421&~~~0.7523\\
\ce{Bi}&~~~0.29838&~~~0.74044&~~~0.55549\\
\ce{Bi}&~~~0.07735&~~~0.1609&~~~0.28045\\
\ce{P}&~~~0.6952&~~~0.0172&~~~0.9215\\
\ce{P}&~~~0.0961&~~~0.372&~~~0.7862\\
\ce{O}&~~~0.3777&~~~0.5382&~~~0.4759\\
\ce{O}&~~~0.3066&~~~0.1549&~~~0.5579\\
\ce{O}&~~~0.859&~~~0.0275&~~~0.8943\\
\ce{O}&~~~0.5569&-0.2084&~~~0.8602\\
\ce{O}&~~~0.621&~~~0.1596&~~~0.7526\\
\ce{O}&~~~0.7684&~~~0.1052&~~~1.1811\\
\ce{O}&~~~0.2584&~~~0.5101&~~~0.7497\\
\ce{O}&-0.0468&~~~0.4637&~~~0.6902\\
\ce{O}&~~~0.0209&~~~0.1498&~~~0.6362\\
\ce{O}&~~~0.1695&~~~0.3727&~~~1.0506\\
\end{array}
$$

and last but not least this renders to an image of:

[![unit cell](https://i.sstatic.net/fwn9n.png)](https://i.sstatic.net/fwn9n.png)

Purple: Bi  
Orange: P  
Red: O


---

### Answer by username_2 on 2019-04-09. Score: 1

Having the same formula does not mean that the crystal structure is the same. An example is calcium carbonate, which can form the minerals calcite or aragonite. So you have to read the publications to know if they have done X-ray diffraction to positively identify the crystals as petitjeanite. If that is the case, then the crystal structure is triclinic and the relevant data can be found at [webmineral.com](http://webmineral.com/data/Petitjeanite.shtml#.XK0Vh_kzZaQ).

ETA: Also note that the unit cell does not necessarily correspond to the visible crystal habit.


---

