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<div class="PlainText">Dear QE Users,<br>
<br>
In order to calculate the total potential along one of the SnSe bonds (Se2-Sn4), I first performed a self-consistent run with the following lattice parameters.<br>
<br>
ibrav=8, celldm(1)=21.34350847, celldm(2)=0.3628777, celldm(3)=0.38586894<br>
<br>
Sn 0.882841736 0.250000000 0.602195343<br>
Sn 0.617158264 0.750000000 0.102195343<br>
Sn 0.382841736 0.250000000 0.897804657<br>
Sn 0.117158264 0.750000000 0.397804657<br>
Se 0.142813748 0.250000000 0.976427467<br>
Se 0.357186252 0.750000000 0.476427467<br>
Se 0.642813748 0.250000000 0.523572533<br>
Se 0.857186252 0.750000000 0.023572533<br>
<br>
I then ran pp.x with the following input:<br>
<br>
&inputpp<br>
prefix = 'SnSe'<br>
filplot = 'potential.dat'<br>
plot_num= 1<br>
/<br>
&plot<br>
iflag=1<br>
output_format=0<br>
nfile = 1<br>
filepp(1) = 'potential.dat'<br>
e1(1)=0.117158264, e1(2)=0.750000000, e1(3)= 0.397804657,<br>
x0(1)=0.357186252, x0(2)= 0.750000000, x0(3)=0.476427467,<br>
nx=100, <br>
fileout= 'VSe2_Sn4.dat’<br>
/<br>
<br>
The bond length is 2.73A=5.16Bohr. Attached is the output of potential vs. distance. The x-axis runs from 0 to ~0.33. According to other links in the Forum, the x-axis is in atomic units. Two possibilities:<br>
<br>
1. The distance is in Bohr. So is the pp.x code plotting from 0 to 0.33 Bohr even though the bond length is 5.16Bohr as defined by the vectors x0 and e1?<br>
2. The distance is in alat. Then 0.33*alat=7.04Bohr. This is longer than the bond length.<br>
<br>
So what is the unit of the x-axis?<br>
<br>
Thank you,<br>
<br>
Vahid<br>
<br>
Vahid Askarpour<br>
Department of Physics and Atmospheric Science<br>
Dalhousie University,<br>
Halifax, NS, Canada<br>
<br>
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