<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;font-family:Calibri,Arial,Helvetica,sans-serif;" dir="ltr">
<p>Hi everyone,</p>
<p><br>
</p>
<p>I am traying to perform a scf calculation for a <span>756 atoms</span> <span>supercell</span> nanoribbon (for a phonon -phonopy- calculation). The problem is that it using the next input:</p>
<p><i><br>
</i></p>
<p><i></i></p>
<div><i>&control<br>
calculation = 'scf'<br>
prefix='grapheneph',<br>
pseudo_dir = './',<br>
outdir='./saleph62/'<br>
/<br>
&system<br>
ibrav = 0,<br>
nat = 756,<br>
ntyp = 1,<br>
occupations = 'smearing',<br>
smearing = 'gaussian',<br>
degauss = 0.01,<br>
ecutwfc = 60.D0,<br>
ecutrho = 500.D0,<br>
/<br>
<div>&electrons<br>
conv_thr = 1.D-8,<br>
diagonalization = 'cg',<br>
mixing_mode = 'plain',</div>
/<br>
K_POINTS gamma<br>
! <b>ibrav = 0, nat = 756, ntyp = 1</b><br>
CELL_PARAMETERS bohr<br>
89.4600000000000080 0.0000000000000000 0.0000000000000000<br>
0.0000000000000000 48.4470000000000027 0.0000000000000000<br>
0.0000000000000000 0.0000000000000000 10.0000000000000000<br>
ATOMIC_SPECIES<br>
C 12.01070 <b>C.pbe-rrkjus.UPF</b><br>
ATOMIC_POSITIONS crystal</i></div>
<p></p>
<p><i>[756 Carbon atoms...]</i><br>
</p>
<p><br>
</p>
<p>Requires <i><span>Estimated max dynamical RAM per process > </span> </i><span><i>64279.60Mb</i></span> of memory, which results in a memory allocation error, since I ''only'' have 65Gb of memory in my computer.</p>
<p>I have already read across this forum and pages from the QE manual, where it suggests using a gamma k-point for instance. But i do not know if this huge amout of memory required is normal, or is due to some absurd input option I am using.
<br>
</p>
<p><br>
</p>
<p>Using <span>electron_maxstep = 50</span> tag does not lead to a memory error, although it is quite slow.</p>
<p><br>
</p>
<p>Solving with this same input for a 1x1x1 supercell (78 atoms), it works perfectly.
<br>
</p>
<p><br>
</p>
<p>Any ideas why I am having this problem? Should I use other input options for this system?</p>
<p><br>
</p>
<p>Thank you for your time and patience.</p>
<p>Pablo.<br>
</p>
<p><br>
</p>
</div>
</body>
</html>