Dear Quantum Espresso users I have done a 'vc-relax' calculation to find the cell parameters of graphite. The selected k-points are (4*4*4) and automatic.
obtained cell parameters: a = 2.469, b = 2.469, c = 7.069, then I used these values to 'relax' the atoms in cell (k-points were 4*4*4 too) . Finally I used the obtained cell parameters to find the proper k-points for graphite. I performed some 'scf' calculations with different k-points and in whole of them the cell parameters and positions were what is obtained from the relax part with 4*4*4 k-points. 'scf' energy with different k-points: k-points energy (4*4*4): -45.5732791969 Ry (5*5*5): -45.57637408 Ry (6*6*6): -45.57592043 Ry (7*7*7): -45.57420434 Ry (8*8*8): -45.57474553 Ry (9*9*9): -45.57500776 Ry (10*10*10): -45.57454272 Ry (11*11*11): -45.57464463 Ry (12*12*12): -45.57480118 Ry (13*13*13): -45.57462800 Ry (14*14*14): -45.57463705 Ry (15*15*15): -45.57473135 Ry (16*16*16): -45.57465384 Ry I appreciate if one help me to find the answers to these questions: 1. Is the whole procedure plausible ?2. why a energy convergence is not occurred after selecting these high values of k-points?3. How can I find the proper k-points safely? the input file for 'scf' calculation: &CONTROL calculation = "scf", pseudo_dir = "/home/koa/soft/qe4.2/espresso-4.2/pseudo", outdir = "/home/koa/tmp", etot_conv_thr= 1.0D-4, forc_conv_thr= 1.0D-3, nstep=150, / &SYSTEM ibrav = 4, a = 2.469, b = 2.469, c = 7.069, cosab = -0.5, cosac = 1.0, cosbc = 1.0, nat = 4, ntyp = 1, ecutwfc = 30.D0, ecutrho = 200.D0 occupations = 'smearing' smearing ='mp', degauss = 0.01, nspin = 2, starting_magnetization(1)= 1.0, / &ELECTRONS conv_thr = 1.D-6, mixing_beta = 0.7D0, diagonalization = "david", / &IONS ion_dynamics="bfgs" / ATOMIC_SPECIES C 12.0107 C.pbe-van_ak.UPF ATOMIC_POSITIONS {angstrom} C 0.000000000 0.000000000 0.000000000 C 0.000000000 1.425534302 0.000000000 C 0.000000000 0.000000000 3.534553118 C 1.234548920 0.712767151 3.534553118 K_POINTS {automatic} 16 16 16 1 1 1 the vc-relax input: &CONTROL calculation = "vc-relax", pseudo_dir = "/home/koa/soft/qe4.2/espresso-4.2/pseudo", outdir = "/home/koa/tmp", etot_conv_thr= 1.0D-4, forc_conv_thr= 1.0D-3, dt=70, nstep=150, / &SYSTEM ibrav = 4, a = 2.456, b = 2.456, c = 6.696, cosab = -0.5, cosac = 1.0, cosbc = 1.0, nat = 4, ntyp = 1, ecutwfc = 30.D0, ecutrho = 200.D0 occupations = 'smearing' smearing ='mp', degauss = 0.01, nspin = 2, starting_magnetization(1)= 1.0, / &ELECTRONS conv_thr = 1.D-6, mixing_beta = 0.7D0, diagonalization = "david", / &IONS ion_dynamics="bfgs" / &CELL cell_dynamics = 'damp-w', press = 0.0 , / ATOMIC_SPECIES C 12.0107 C.pbe-van_ak.UPF ATOMIC_POSITIONS {angstrom} C 0.00000000 0.00000000 0.00000000 C 0.00000000 1.41797226 0.00000000 C 0.00000000 0.00000000 3.34800000 C 1.22800000 0.70898613 3.34800000 K_POINTS {automatic} 4 4 4 1 1 1 very best wishes Many ThanksMasoud NahaliSharif University of Technology _________________________________________________________________ Hotmail: Trusted email with Microsoft?s powerful SPAM protection. https://signup.live.com/signup.aspx?id=60969 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20100630/19e3127c/attachment.htm