[Pw_forum] Quick question on coordinates
Miguel Martinez
miguel.martinez at ehu.es
Tue Feb 26 19:55:18 CET 2008
Dear colleages,
I'm currently doing some stuff on face-centered monoclinic structures, and
have found silly problems. For example, the documentation reads:
espresso/Doc/INPUT_PW:
monoclinic (p)
=============================
a1 = (a,0,0), a2= (b*sin(gamma), b*cos(gamma), 0), a3 = (0, 0, c)
where gamma is the angle between axis a and b
base centered monoclinic
=============================
a1 = ( a/2, 0, -c/2),
a2 = (b*cos(gamma), b*sin(gamma), 0),
a3 = ( a/2, 0, c/2),
¿Is it right? ¿Is it a typo? I fear it's a typo, because changing ibrav
from 12 to 13 decreases cell volume by exactly a factor of 2. What's more,
\vec{a}*\vec{b}=|a|*|b|*cos(ab),
while according to the basis in the monoclinic case we'd have
\vec{a}*\vec{b}=|a|*|b|*sin(ab)
Thanks in advance,
Miguel
--
----------------------------------------
Miguel Martínez Canales
Dto. Física de la Materia Condensada
UPV/EHU
Facultad de Ciencia y Tecnología
Apdo. 644
48080 Bilbao (Spain)
Fax: +34 94 601 3500
Tlf: +34 94 601 5326
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