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<style>.hmmessage P{margin:0px;padding:0px}body.hmmessage{FONT-SIZE: 10pt;FONT-FAMILY:Tahoma}</style>Dear all,<br><br>I'm doing anatase 001 surface relaxation using different pseudo cutoff. But the surface structure depending<br>strongly on pseudo cutoff.<br>For example, when I set ecutwfc=30 Ry and ecutrho=240 Ry for the calculation, the relaxed structure is<br>ATOMIC_POSITIONS (angstrom)<br>Ti 0.000019234 0.000016929 5.241338958<br>Ti 1.896866310 1.894973881 0.424606117<br>Ti -0.002611826 1.894973568 7.609344136<br>Ti 1.894935792 0.000016645 2.794368221<br>O -0.000497095 1.894979291 5.668409409<br>O 0.000892662 0.000020764 7.220228726<br>O 1.897822837 1.894975309 8.112610082<br>O -0.002069692 1.894975762 -0.077265872<br>O 1.894316864 0.000021111 0.814634124<br>O 1.895351386 1.894979829 2.365218854<br>O 0.000036842 0.000033726 3.235875667<br>O 1.894936685 0.000033184 4.800631577<br><br>when I set ecutwfc=50 Ry and ecutrho=400 Ry for the same calculation, the relaxed structure is <br><br>ATOMIC_POSITIONS (angstrom)<br>Ti 0.022799298 0.000081081 5.241509392<br>Ti 1.936096642 1.894995998 0.443063583<br>Ti -0.037388794 1.894978067 7.592310260<br>Ti 1.868524560 -0.000008072 2.794849232<br>O -0.102420723 1.894969978 5.654104817<br>O 0.193587382 0.000011079 7.215460406<br>O 2.107237211 1.894969616 8.171152812<br>O -0.209955519 1.895019689 -0.141004735<br>O 1.700007345 0.000017676 0.820240249<br>O 1.998867848 1.894956901 2.381473163<br>O 0.007469691 0.000019075 3.237525157<br>O 1.885175059 -0.000011088 4.799315665<br><br>unfortunately this forum is not support pictures or pdf files, I can't display it in photos. I'll illustrate <br>the big difference in structure of the calculations only by word.<br><br>In the case of ecutwfc=30 Ry and ecutrho=240 Ry, there is a the mirror plane symmetry along <br>the [100] direction. The two Ti-O bonds on surface is about 1.964 Angstrom and the angle of <br>surface O-Ti-O atoms is about 150.269 degrees. The structure is consistent well with the literature<br>(figure SI in supporting information of J. Phys. Chem. B 2006, 110, 2804-2811). But the my calculated s<br>urface energy is 1.06049 J/m^2, which is about 8% higher than the literature.<br><br>I think the surface energy difference may be because of the ecutwfc and ecutrho. So I increased it to <br>higher value, ecutwfc=50 Ry and ecutrho=400 Ry. But the calculated structure with this cutoff is so surprising. <br>As shown above, the mirror plane symmetry along the [100] direction is broken: the two O-Ti bonds on <br>the surface become strongly inequivalent, with bond lengths of 1.74 and 2.22 angstrom. And the angle of <br>surface O-Ti-O atoms is about 145.508 degrees. Even from the coordinate of each atom is quite different in <br>the two cases. I also find this kind of structure reported by literature Physical Review letters, 2001, 87, 266105. <br>But my calculated structure parameters is about 1% errors, and energetic parameters is about 6% errors with <br>respect to the literature.<br><br><br>For my two tested case the structure is so greatly depending on the cutoff. I think the higher cutoff must be more accurate.<br>So there may be something inaccurate with the former case and the literature J. Phys. Chem. B 2006, 110, 2804-2811, <br>because of the smaller cutoff.<br>How do you think about it? <br>And Why my calculated energy is ~6-8% different than the literature.<br><br>Here is my input file<br><br> &CONTROL<br> title = 'Anatase 001' ,<br> calculation = 'relax' ,<br> restart_mode = 'from_scratch' ,<br> outdir = '/home/vega/TiO2/Anatase/001/relaxtest/tmp/' ,<br> wfcdir = '/tmp/' ,<br> pseudo_dir = '/home/vega/espresso-4.0/pseudo/' ,<br> prefix = 'Anatase 001 1X1' ,<br> disk_io = 'none' ,<br> etot_conv_thr = 0.0005 ,<br> forc_conv_thr = 0.0011668141375 ,<br> nstep = 1000 ,<br> /<br> &SYSTEM<br> ibrav = 6,<br> celldm(1) = 7.1619,<br> celldm(3) = 4.7591,<br> nat = 12,<br> ntyp = 2,<br> ecutwfc = 30 , #ecutwfc=50 for later case<br> ecutrho = 240 , #ecutrho=400 for later case<br> /<br> &ELECTRONS<br> conv_thr = 1.0D-8 ,<br> /<br> &IONS<br> ion_dynamics = 'bfgs' ,<br> /<br>ATOMIC_SPECIES<br> Ti 47.86700 Ti.pw91-sp-van_ak.UPF <br> O 15.99940 O.pw91-van_ak.UPF <br>ATOMIC_POSITIONS angstrom <br> Ti 0.000000000 0.000000000 5.220000000 <br> Ti 1.895000000 1.895000000 0.410000000 <br> Ti 0.000000000 1.895000000 7.625000000 <br> Ti 1.895000000 0.000000000 2.815000000 <br> O 0.000000000 1.895000000 5.630000000 <br> O 0.000000000 0.000000000 7.214000000 <br> O 1.895000000 1.895000000 8.036000000 <br> O 0.000000000 1.895000000 0.000000000 <br> O 1.895000000 0.000000000 0.820000000 <br> O 1.895000000 1.895000000 2.404000000 <br> O 0.000000000 0.000000000 3.226000000 <br> O 1.895000000 0.000000000 4.810000000 <br>K_POINTS automatic <br> 4 4 1 1 1 1 <br><br>Thank you for reading. looking forward to your reply.<br><br><font size="4"><span style="font-family: Lucida Handwriting,Cursive;">Vega Lew</span></font><br>PH.D Candidate in Chemical Engineering<br>State Key Laboratory of Materials-oriented Chemical Engineering<br>College of Chemistry and Chemical Engineering<br>Nanjing University of Technology, 210009, Nanjing, Jiangsu, China<br /><hr />Discover the new Windows Vista <a href='http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE' target='_new'>Learn more!</a></body>
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