<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" style="display:none;"><!-- P {margin-top:0;margin-bottom:0;} --></style>
</head>
<body dir="ltr">
<div id="divtagdefaultwrapper" style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>Dear all,</p>
<p><br>
</p>
<p>I am trying to perform some calculations on Black Phosphorus (BP). To get the atomic positions I used the Crystal Builder, where I have chosen the lattice type to be base centered orthorhombic. The "builder" produced a set of cartesian and fractional (in
terms of the primitive cell vectors) . I have used the fractional ones and I have also used ibrav=0 with the CELL_PARAMETERS defined as in the builder (a/2, -b/2, 0), (a/2, b/2,0), (0,0,c). However I have got the following error:</p>
<p><br>
</p>
<p></p>
<div> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</div>
<div> from check_atoms : error # 1</div>
<div> atoms # 1 and # 4 overlap!</div>
<div> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</div>
<div><br>
</div>
Doing the same calculation with ibrav=8 and using the coordinates produced by the Crystal builder for a simple orthorhombic does not produce any errors. Can anyone please tell me what is wrong with atoms (1) and (4). Is BP simple or base centered orthorhombic..Where
can I find the coorect atomic position of bulk BP? The scf input is below:
<p></p>
<p><br>
</p>
<p> </p>
<div>&CONTROL</div>
<div> prefix='bp',</div>
<div> calculation='scf',</div>
<div> restart_mode='from_scratch',</div>
<div> wf_collect=.true.,</div>
<div> forc_conv_thr=1.D-4</div>
<div> etot_conv_thr=1.D-5</div>
<div> tstress=.true.,</div>
<div> tprnfor=.true.,</div>
<div> pseudo_dir ='/home_cluster/fis718/elio/espresso-4.1.3/pseudo',</div>
<div> outdir='/home_cluster/fis718/elio/espresso-4.1.3/BP/OUT'</div>
<div> /</div>
<div> &SYSTEM</div>
<div> ibrav=0,celldm(1)=6.26179,nat=8, ntyp= 1, ecutwfc=10, ecutrho=40, occupations='smearing', london=.true., smearing='mp', degauss=0.035,nbnd=32</div>
<div>/</div>
<div> &ELECTRONS</div>
<div> conv_thr=1.D-8,</div>
<div> mixing_beta=0.1</div>
<div>/</div>
<div>&IONS</div>
<div>ion_dynamics='bfgs'</div>
<div>/</div>
<div>&CELL</div>
<div>cell_dynamics='bfgs'</div>
<div>press=0.0</div>
<div>/</div>
<div>ATOMIC_SPECIES</div>
<div>P 30.97376 P.pbe-n-van.UPF</div>
<div>ATOMIC_POSITIONS crystal</div>
<div>P -0.89832 0.89832 0.91944</div>
<div>P -0.39832 0.39832 0.58056</div>
<div>P -0.10168 0.10168 0.08056</div>
<div>P 0.10168 0.89832 0.91944</div>
<div>P -0.10168 1.10168 0.08056</div>
<div>P -0.60168 0.60168 0.41944</div>
<div>P -0.39832 1.39832 0.58056</div>
<div>P 0.39832 0.60168 0.41944</div>
<div><br>
</div>
<div>K_POINTS automatic</div>
<div> 2 2 2 0 0 0</div>
<div><br>
</div>
<div>CELL_PARAMETERS alat</div>
<div>0.5000 -1.58106 0.0000</div>
<div>0.500 1.58106 0.0000</div>
<div>0.0000 0.00000 4.3763</div>
<div><br>
</div>
<div><br>
</div>
<div>thanks</div>
<div><br>
</div>
<div>Elio Arbid</div>
<div>University of Nottingham</div>
<div>UK</div>
<p></p>
</div>
</body>
</html>