<div dir="ltr"><div>Maybe the question was about the definition of such matrix (since it is not symmetric, it is a legitimate question). The three rows are the cartesian coordinates of the three primitive vectors of the lattice. The following piece of code I wrote some time ago should convert from lattice vectors to crystalographic parameters (no warranty)<br><br>Paolo<br><br>subroutine cell2abc ( alat, at, a,b,c,cosab,cosac,cosbc )<br> !<br> ! returns crystallographic parameters a,b,c from lattice vectors<br> !<br> USE kind, ONLY: dp<br> USE constants, ONLY: bohr_radius_angs<br> IMPLICIT NONE<br> !<br> REAL(DP), INTENT (IN) :: alat, at(3,3)<br> REAL(DP), INTENT (OUT) :: a,b,c, cosab, cosac, cosbc <br> REAL(DP) :: norm1, norm2, norm3<br> !<br> !<br> norm1 = SQRT ( at(1,1)**2 + at(2,1)**2 + at(3,1)**2 )<br> norm2 = SQRT ( at(1,2)**2 + at(2,2)**2 + at(3,2)**2 )<br> norm3 = SQRT ( at(1,3)**2 + at(2,3)**2 + at(3,3)**2 )<br> !<br> a = alat * norm1 / bohr_radius_angs<br> b = alat * norm2 / bohr_radius_angs<br> c = alat * norm3 / bohr_radius_angs<br> !<br> cosab = (at(1,1)*at(1,2) + at(2,1)*at(2,2) + at(3,1)*at(3,2))/norm1/norm2<br> cosac = (at(1,1)*at(1,3) + at(2,1)*at(2,3) + at(3,1)*at(3,3))/norm1/norm3<br> cosbc = (at(1,3)*at(1,2) + at(2,3)*at(2,2) + at(3,3)*at(3,2))/norm3/norm2<br><br> !<br>END SUBROUTINE cell2abc<br><br></div>Paolo<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, May 6, 2015 at 2:25 PM, Giuseppe Mattioli <span dir="ltr"><<a href="mailto:giuseppe.mattioli@ism.cnr.it" target="_blank">giuseppe.mattioli@ism.cnr.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Dear Francesco<br>
<br>
> CELL_PARAMETERS (alat= 9.37304158)<br>
> *_0.998026269_* 0.000004734 -0.013893833<br>
> 0.000009261 _*1.956757114*_ -0.000006827<br>
> -0.117999199 -0.000006751 *_1.878825464_*<br>
<br>
This is a matrix containing the projections of the optimized lattice parameters on the cartesian axes in alat units (alat=9.37304158 bohr). If you<br>
want your alpha-beta-gamma angles you can calculate them. If you are lazy (I usually am with nonorthogonal cells...) you may open the pw.x output with<br>
xcrysden and figure out the values with the angle-measurement tool.<br>
<br>
HTH<br>
Giuseppe<br>
<span class=""><br>
On Wednesday, May 06, 2015 12:41:09 PM Francesco Pelizza wrote:<br>
> Hi to everyone,<br>
><br>
> I am sorry to bother for such a simple question, but I need to be sure<br>
> about what QE is giving me in the OUTPUT file.<br>
><br>
> After a VC-relaxation on a cell with angles with one or more of alpha<br>
> beta gamma angles different from 90°, the VC-relaxation OUTPUT file<br>
> gives out this:<br>
><br>
> CELL_PARAMETERS (alat= 9.37304158)<br>
</span>> *_0.998026269_* 0.000004734 -0.013893833<br>
> 0.000009261 _*1.956757114*_ -0.000006827<br>
> -0.117999199 -0.000006751 *_1.878825464_*<br>
<span class="">><br>
> The Bold and underlined values are the new Alat, Blat and Clat factor to<br>
> multiplicate the old alat given, to have the new cell dimension in bohrs.<br>
><br>
> But I guess the other numbers are giving me the alpha beta and gamma<br>
> angles (celldm 4-5-6)....<br>
><br>
> But who is who?<br>
><br>
> Thank you very much for reading!<br>
><br>
> Francesco Pelizza<br>
<br>
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