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<BODY><P>Dear advanced users and developers of PWSCF;</P>
<P> </P>
<P>I recently installed Quantum Espresso code, ver 3.2.2, and </P>
<P>performed simple calculations for tests using PWSCF. </P>
<P>Today, I have found that total energy of a single oxygen atom</P>
<P>calculated in PWSCF is different from that generated in Vanderbilt's </P>
<P>pseudopotential code (ver. 7.3.6). I surely remember that the total</P>
<P>energies of single atom in pseudopotential generation program</P>
<P>and in plane wave code are almost same within small errors, when</P>
<P>I used Berkely code made by S. Froyen. Please inform me if I make</P>
<P>any mistake in using PWSCF code, after seeing following results.</P>
<P> </P>
<P>1. Total energy of a single oxygen atom calculated by Vanderbilt's </P>
<P>pseudopotential code;</P>
<P> </P>
<P>You can easily find it in the header of the oxygen pseudopotential file</P>
<P>O.pbe-van_bm.UPF at PWSCF webpage, as follows. </P>
<P> </P>
<P><PP_HEADER><BR> 0 Version Number<BR> O Element<BR> US Ultrasoft pseudopotential<BR> F Nonlinear Core Correction<BR> SLA PW PBE PBE PBE Exchange-Correlation functional<BR> 6.00000000000 Z valence<BR> -31.58339463984 Total energy<BR> 25.000000 100.0000000 Suggested cutoff for wfc and rho<BR> 1 Max angular momentum component<BR> 737 Number of points in mesh<BR></P>
<P>Thus, this file indicate that the total energy of single oxygen atom is </P>
<P>-31.58339463984 Ry. </P>
<P> </P>
<P>2. PWSCF calculation</P>
<P> </P>
<P>I used following input file. </P>
<P> </P>
<P>&control<BR> calculation='relax',<BR> restart_mode='from_scratch',<BR> prefix='o',<BR> pseudo_dir = '/home/kgna0022/pseudo/',<BR> outdir='/scratch2/kgna0022/tmp/',<BR> nstep=1,<BR> /<BR> &system<BR> ibrav= 1,<BR> celldm(1)=20.0<BR> nat= 1, ntyp= 1,<BR> ecutwfc =30.0,<BR> ecutrho =210.0,<BR> nbnd=6,<BR> occupations='from_input',<BR> /<BR> &electrons<BR> conv_thr = 1.0D-8,<BR> mixing_beta = 0.7D0,<BR>/<BR>&IONS<BR> pot_extrapolation = "second_order",<BR> wfc_extrapolation = "second_order",<BR>/<BR>ATOMIC_SPECIES<BR> O 16.00 O.pbe-van_bm.UPF<BR>ATOMIC_POSITIONS (bohr)<BR>O 0.00000000000 0.000000000 0.000000000<BR>K_POINTS (Gamma)<BR>OCCUPATIONS<BR>2.0 1.333333333333333 1.333333333333333 1.333333333333333 0.0 0.0<BR></P>
<P>After running PWSCF, I obtained following results.</P>
<P> </P>
<P> total energy = -31.53644545 Ry<BR> total energy = -31.53655807 Ry<BR> total energy = -31.53657629 Ry<BR>! total energy = -31.53657705 Ry<BR></P>
<P>Thus, the total energy is -31.53657705 Ry, diffent from</P>
<P>the result of Vanderbilt's code, -31.58339463984 Ry. </P>
<P> </P>
<P>If you teach me my mistake during the calculations, I will</P>
<P>be happy. However, if you don't find my mistake, I cordially ask </P>
<P>developers of PWSCF code to solve this problem.</P>
<P>Thank you very much.</P>
<P> </P>
<P>Best regards,</P>
<P> </P>
<P>Eun-Cheol Lee, Ph. D.</P>
<P>Assistant Professor,</P>
<P>Dept. of BioNano Tech., </P>
<P>Kyungwon University, Korea.</P>
<P>E-mail : <A href="mailto:eclee@kyungwon.ac.kr">eclee@kyungwon.ac.kr</A></P>
<P>TEL : +82-31-750-8752</P>
<P> </P>
<img src="http://mail.kyungwon.ac.kr/cgi-bin/setconfirm.cgi?k=1181660944913115516115&u=eclee&d=kyungwon.ac.kr" width=1 height=1>
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