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On 25/05/17 07:19, Charlie Ruffman wrote:<br>
<blockquote type="cite"
cite="mid:ME1PR01MB201809DA6A234525E93DB8AC8BFF0@ME1PR01MB2018.ausprd01.prod.outlook.com">
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<div id="divtagdefaultwrapper" style="font-size: 12pt; color:
rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica,
sans-serif, EmojiFont, "Apple Color Emoji",
"Segoe UI Emoji", NotoColorEmoji, "Segoe UI
Symbol", "Android Emoji", EmojiSymbols,
EmojiFont, "Apple Color Emoji", "Segoe UI
Emoji", NotoColorEmoji, "Segoe UI Symbol",
"Android Emoji", EmojiSymbols, EmojiFont, "Apple
Color Emoji", "Segoe UI Emoji", NotoColorEmoji,
"Segoe UI Symbol", "Android Emoji",
EmojiSymbols;" dir="ltr">On a related topic, we were interested
in how the choice of supercell size might influence the
vibrational modes we calculate. For instance, looking at a the
smallest repeatable unit of our system naturally yields fewer
vibrational modes than simulating a cell of 2 or 3 times the
size. We were wondering whether allowing the extra freedom
associated with a larger cell might actually map worse
onto experimental results? <br>
</div>
</blockquote>
<br>
Hi,<br>
unless there is something that breaks symmetry (like a defect,
substitution, long-range spin order, charge density wave...) the
supercell will give exactly the same result as the unit cell. It is
even possible to map (aka unfold) the supercell phonon dispersion to
the unit cell one, although I cannot recall the name of any specific
tool that does it at this moment.<br>
<br>
regards<br>
<br>
<pre class="moz-signature" cols="72">--
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 442 79822 / skype: paulatz
www: <a class="moz-txt-link-freetext" href="http://www-int.impmc.upmc.fr/~paulatto/">http://www-int.impmc.upmc.fr/~paulatto/</a>
mail: 23-24/423 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05</pre>
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