[QE-users] units of q points in matdyn.in files to calculate phonon dispersion

[Hari Paudyal]

Hi,

You can define "q_in_cryst_coord = .TRUE." in your matdyn.in file.

Best,
Hari Paudyal
SUNY Binghamton

On Sun, Oct 27, 2019 at 9:06 PM w <west_lifer at 163.com> wrote:

> It is my pleasure to write to you.
> I am a postgraduate student in Tsinghua university.
> I am calculating phonon dispersion  with quantum espresso.
> And I am using materialscloud to creat K ponits on line.
> I would like to ask some questions about units of q points in
> matdyn.in.freq files.
> For example , H point for MgB2 , is (0.3333 0.3333 0.5) with scaled units
> created on materialscloud or using Materials Studio.
> My question is whether H (0.3333 0.3333 0.5)  be used directly in
> matdyn.in files to calculate phonon dispersion.
> In the matdyn.in files , Kpoint's unit is  "2pi/alat" ,so it's wrong to
> use H (0.3333 0.3333 0.5) directly?
>
> So I convert H (0.3333 0.3333 0.5) to （0.333333  0.57735  0.437548）with
> 2pi/alat units , and here is my ways,I don't konw whether it's right ？ Or
> how to convert it ?
> First , scf.out contains information about "reciprocal axes: (cart. coord.
> in units 2 pi/alat)", it's
> b(1) = (  1.000000  0.577350 -0.000000 )
> b(2) = (  0.000000  1.154701  0.000000 )
> b(3) = (  0.000000 -0.000000  0.875096 )
> Then , H point with scaled units is ( 0.3333 0.3333 0.5 ) ,
> equals to  0.3333*b(1）+0.3333*b(2)+0.5*b(3)  with unit 2pi/alat，
> because in scf.out files :
>               b(1)= 1*2pi/alat(1)+0.577350*2pi/alat(2)+0*2pi/alat(3),
>               b(2)= 0*2pi/alat(1)+1.154701*2pi/alat(2)+0*2pi/alat(3),
>               b(3)= 0*2pi/alat(1)+0*2pi/alat(2)+0.875096*2pi/alat(3),
> Finally, H points convert to （0.333333   0.57735      0.437548）with unit
> 2pi/alat,
> which equals to row vector H multify matrix B=[ b(1) ; b(2) ; b(3) ]
>  = H*B=（0.333333  0.57735  0.437548）with 2pi/alat units.
> Is this the right method to convert high symmetry q points ?
> Or how to convert the q points with scaled units to those with 2pi/alat?
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