<br>Dear Kajal,<br><br>besides the fact that the isolated Zn is not really isolated in your calculations there are some other <br>few things you may want to check.<br><br>1) ecutrho is normally larger than 5*ecutwfc for US PPs (typically 8* or more). did you check convergence of energy (at least) and maybe forces wrt this parameter?<br>
<br>2) do you really need such a small smearing and such a fine k-point grid?<br><br>3) conv_thr seems a bit high to me.<br><br>hth<br><br>Matteo<br><br><br><br><div class="gmail_quote">On Thu, Nov 11, 2010 at 6:32 AM, kajal jindal <span dir="ltr"><<a href="mailto:kajalmh18@gmail.com">kajalmh18@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hi all,<div><br></div><div>I am calculating the cohesive energy of Zn and I am getting a value of -0.734 eV which is almost 50% of the experimental value of -1.35 eV.Can anybody plz suggest me what is going wrong with my calculation...I read the forum regarding it but still unable to resolve my problem..</div>
<div>Following are the input files that i used for the calculation of total energy of bulk Zn atom in the hexagonal crystal structure and isolated Zn atom respectively..</div><div>/* input file for bulk Zn atom in crystal */</div>
<div><div> &control</div><div> calculation='scf',</div><div> restart_mode='from_scratch',</div><div> prefix='bZn'</div><div> wf_collect=.true.,</div><div> pseudo_dir = '/home/kajaljindal/pseudo/',</div>
<div> outdir= './'</div><div>/</div><div> &system</div><div> ibrav = 4, nat= 2, ntyp= 1,celldm(1) = 5.0338, celldm(3) = 1.85829,</div><div> ecutwfc = 60.0,ecutrho=300, occupations ='smearing',smearing='m-v',</div>
<div> degauss=0.001,starting_magnetization(1)=0.5,nspin=2,nosym=.true.,</div><div>/</div><div> &electrons</div><div> mixing_beta = 0.1</div><div> mixing_mode = 'local-TF'</div><div> mixing_ndim = 10</div>
<div> conv_thr = 1.0e-5</div><div> diagonalization = 'david'</div><div>/</div><div><br></div><div>ATOMIC_SPECIES</div><div> Zn 65.39 Zn.pbe-van.UPF</div><div><br></div><div>ATOMIC_POSITIONS {crystal}</div>
<div>Zn 0.333333 0.666666997 0.249999990</div><div>Zn 0.666667 0.333333003 0.750000010</div><div><br></div><div>K_POINTS {automatic}</div><div> 9 9 6 0 0 0</div></div><div><br></div><div>/* part of the corresponding output file */</div>
<div><div> total energy = -253.16323313 Ry</div><div> Harris-Foulkes estimate = -253.16322516 Ry</div><div> estimated scf accuracy < 0.00000202 Ry</div><div><br></div><div> The total energy is the sum of the following terms:</div>
<div><br></div><div> one-electron contribution = -133.25510851 Ry</div><div> hartree contribution = 94.29714101 Ry</div><div> xc contribution = -37.02058576 Ry</div><div> ewald contribution = -177.18467547 Ry</div>
<div> smearing contrib. (-TS) = -0.00000441 Ry</div><div><br></div><div> total magnetization = 0.00 Bohr mag/cell</div><div> absolute magnetization = 0.00 Bohr mag/cell</div></div><div>
<br></div><div>/* input file for isolated atom */</div><div><div>&control</div><div> calculation='scf',</div><div> restart_mode='from_scratch',</div><div> prefix='iZn'</div><div> wf_collect=.true.,</div>
<div> pseudo_dir = '/home/kajaljindal/pseudo/',</div><div> outdir= './'</div><div>/</div><div> &system</div><div> ibrav = 4, nat= 1, ntyp= 1,celldm(1) = 5.0338, celldm(3) = 1.85829,</div><div>
ecutwfc = 60.0,ecutrho=300, occupations ='smearing',smearing='m-v',</div><div> degauss=0.001,starting_magnetization(1)=0.5,nspin=2,nosym=.true.,</div><div> /</div><div> &electrons</div><div> mixing_beta = 0.1</div>
<div> mixing_mode = 'local-TF'</div><div> mixing_ndim = 10</div><div> conv_thr = 1.0e-5</div><div> diagonalization = 'david'</div><div> /</div><div>ATOMIC_SPECIES</div><div> Zn 65.39 Zn.pbe-van.UPF</div>
<div><br></div><div>ATOMIC_POSITIONS {crystal}</div><div>Zn 0.0 0.0 0.0</div><div><br></div><div>K_POINTS {automatic}</div><div> 9 9 6 0 0 0</div></div><div><br></div><div>/* part of the corresponding output file */</div>
<div><div> total energy = -126.55461784 Ry</div><div> Harris-Foulkes estimate = -126.55460743 Ry</div><div> estimated scf accuracy < 0.00000039 Ry</div><div><br></div><div> The total energy is the sum of the following terms:</div>
<div><br></div><div> one-electron contribution = -125.24932971 Ry</div><div> hartree contribution = 73.37661809 Ry</div><div> xc contribution = -18.43093183 Ry</div><div> ewald contribution = -56.25098076 Ry</div>
<div> smearing contrib. (-TS) = 0.00000637 Ry</div><div><br></div><div> total magnetization = 0.00 Bohr mag/cell</div><div> absolute magnetization = 0.00 Bohr mag/cell</div></div><div>
<br></div><div>I deduced twice the total energy for the isolated Zn atom from the energy for the bulk Zn atom in crystal to obtain the cohesive energy...Plz guide me where am i going wrong....</div><div><br></div><div>Thanks in advance..</div>
<div><span style="font-family: arial,sans-serif; font-size: 13px; border-collapse: collapse;">sincerely,<br>Miss Kajal<br>(UTA)(University of Delhi)<br>Junior Research Fellow<br></span></div><div>
<span style="font-family: arial,sans-serif; font-size: 13px; border-collapse: collapse;"><br></span></div>
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<br></blockquote></div><br><br clear="all"><br>-- <br><font color="#888888">Matteo Cococcioni<br>
Department of Chemical Engineering and Materials Science,<br>
University of Minnesota<br>
421 Washington Av. SE<br>
Minneapolis, MN 55455<br>
Tel. +1 612 624 9056 Fax +1 612 626 7246</font><br>