Dear users I have used 5.1.1 version to optimize conventional cell of CeO2 with 12 atoms. I used PSLIBRARY to use USPP for Ce and O atoms. Here is my input for CeO2 conventional cell: ================== &CONTROL title = 'CeO2' calculation = 'vc-relax' restart_mode = 'from_scratch' outdir = './ceo2_vc_relax' pseudo_dir = './' prefix = 'ceo2' disk_io = 'default' verbosity = 'default' etot_conv_thr=1.0D-9 forc_conv_thr=1.0D-4 nstep=1000 wf_collect=.true. / &SYSTEM ibrav = 0 nat = 12 ntyp = 2 ecutwfc = 173 ecutrho = 692 starting_magnetization(1)=0.5 starting_magnetization(3)=0.5 nspin=2 occupations='smearing' degauss=0.001 smearing='mv' nbnd=82 / &ELECTRONS electron_maxstep = 1000 conv_thr = 1.0D-10 mixing_mode = 'plain' mixing_beta = 0.4 mixing_ndim = 8 diagonalization = 'david' / &IONS ion_dynamics = 'bfgs' / &CELL cell_dynamics = 'bfgs' / ATOMIC_SPECIES O 15.9989995956 O.pbe-nl-rrkjus_psl.1.0.0.UPF Ce 140.1199951172 Ce.pbe-spdfn-rrkjus_psl.1.0.0.UPF
ATOMIC_POSITIONS crystal O 0.2500000000000000 0.2499999999999999 0.2499999999999999 O 0.7500000000000000 0.7499999999999999 0.2499999999999999 O 0.7500000000000000 0.2499999999999999 0.7499999999999999 O 0.2500000000000000 0.7499999999999999 0.7499999999999999 O 0.2500000000000000 0.2499999999999999 0.7499999999999999 O 0.7500000000000000 0.7499999999999999 0.7499999999999999 O 0.7500000000000000 0.2499999999999999 0.2499999999999999 O 0.2500000000000000 0.7499999999999999 0.2499999999999999 Ce 0.0000000000000000 0.0000000000000000 0.0000000000000000 Ce 0.0000000000000000 0.4999999999999999 0.4999999999999999 Ce 0.5000000000000000 0.0000000000000000 0.4999999999999999 Ce 0.5000000000000000 0.4999999999999999 0.0000000000000000 K_POINTS automatic 3 3 3 0 0 0 CELL_PARAMETERS 10.225308105044215 0.000000000000000 0.000000000000000 0.000000000000000 10.225308105044215 0.000000000000000 0.000000000000000 0.000000000000000 10.225308105044215 ==================================================== Everything is OK for conventional cell vc-relax command (very low force and stress). My problem is for slab optimization. I used following command to relax 2*2 110 surface slab with 6 layers and 4 bottom layers fixed. You can see my input: =================================================== &CONTROL title = 'ceo2_110' calculation = 'relax' restart_mode = 'from_scratch' outdir = './ceo2_110' pseudo_dir = './' prefix = 'ceo2_110' disk_io = 'default' verbosity = 'default' tstress = .true. tprnfor = .true. etot_conv_thr=1.0D-9 forc_conv_thr=1.0D-4 nstep=1000 wf_collect=.true. / &SYSTEM ibrav = 0 nat = 72 ntyp = 2 ecutwfc = 173 ecutrho = 692 starting_magnetization(1)=0.5 starting_magnetization(3)=0.5 nspin=2 occupations='smearing' degauss=0.001 smearing='mv' nbnd=490 / &ELECTRONS electron_maxstep = 1000 conv_thr = 1.0D-10 mixing_mode = 'plain' mixing_beta = 0.4 mixing_ndim = 8 diagonalization = 'david' / &IONS ion_dynamics = 'bfgs' / ATOMIC_SPECIES O 15.9989995956 O.pbe-nl-rrkjus_psl.1.0.0.UPF Ce 140.1199951172 Ce.pbe-spdfn-rrkjus_psl.1.0.0.UPF ATOMIC_POSITIONS crystal O 0.1250000000000000 -0.0000000000000000 0.0000000000000003 0 0 0 O 0.1250000000000000 -0.0000000000000000 0.1562436466930924 0 0 0 O 0.1250000000000001 0.0000000000000001 0.3124872933861844 O 0.3750000000000002 0.2499999999999999 0.2343654700396384 0 0 0 O 0.3750000000000002 0.2499999999999999 0.0781218233465463 0 0 0 O 0.3750000000000002 0.2500000000000000 0.3906091167327304 O 0.3750000000000002 0.0000000000000001 0.0000000000000003 0 0 0 O 0.3750000000000001 -0.0000000000000002 0.1562436466930924 0 0 0 O 0.3750000000000003 0.0000000000000001 0.3124872933861844 O 0.1250000000000001 0.2499999999999999 0.2343654700396383 0 0 0 O 0.1250000000000001 0.2500000000000001 0.0781218233465462 0 0 0 O 0.1250000000000001 0.2500000000000000 0.3906091167327304 O 0.6250000000000002 -0.0000000000000001 0.0000000000000003 0 0 0 O 0.6250000000000002 -0.0000000000000001 0.1562436466930924 0 0 0 O 0.6250000000000002 0.0000000000000000 0.3124872933861844 O 0.8750000000000002 0.2499999999999998 0.2343654700396384 0 0 0 O 0.8750000000000002 0.2499999999999998 0.0781218233465463 0 0 0 O 0.8750000000000002 0.2499999999999999 0.3906091167327304 O 0.8750000000000002 -0.0000000000000001 0.0000000000000003 0 0 0 O 0.8750000000000001 -0.0000000000000001 0.1562436466930924 0 0 0 O 0.8750000000000004 0.0000000000000000 0.3124872933861845 O 0.6250000000000002 0.2499999999999999 0.2343654700396384 0 0 0 O 0.6250000000000002 0.2500000000000002 0.0781218233465463 0 0 0 O 0.6250000000000002 0.2500000000000001 0.3906091167327304 O 0.1250000000000000 0.4999999999999999 0.0000000000000003 0 0 0 O 0.1250000000000000 0.5000000000000001 0.1562436466930923 0 0 0 O 0.1250000000000001 0.5000000000000001 0.3124872933861844 O 0.3750000000000002 0.7500000000000000 0.2343654700396384 0 0 0 O 0.3750000000000002 0.7499999999999999 0.0781218233465463 0 0 0 O 0.3750000000000002 0.7500000000000000 0.3906091167327304 O 0.3750000000000002 0.5000000000000001 0.0000000000000002 0 0 0 O 0.3750000000000001 0.4999999999999999 0.1562436466930924 0 0 0 O 0.3750000000000004 0.5000000000000001 0.3124872933861843 O 0.1250000000000001 0.7500000000000000 0.2343654700396383 0 0 0 O 0.1250000000000001 0.7500000000000001 0.0781218233465462 0 0 0 O 0.1250000000000001 0.7500000000000002 0.3906091167327304 O 0.6250000000000003 0.4999999999999999 0.0000000000000002 0 0 0 O 0.6250000000000001 0.5000000000000001 0.1562436466930923 0 0 0 O 0.6250000000000003 0.5000000000000001 0.3124872933861844 O 0.8750000000000002 0.7500000000000000 0.2343654700396384 0 0 0 O 0.8750000000000002 0.7499999999999999 0.0781218233465463 0 0 0 O 0.8750000000000002 0.7500000000000001 0.3906091167327304 O 0.8750000000000002 0.5000000000000001 0.0000000000000002 0 0 0 O 0.8750000000000000 0.4999999999999999 0.1562436466930924 0 0 0 O 0.8750000000000006 0.5000000000000001 0.3124872933861844 O 0.6250000000000002 0.7500000000000001 0.2343654700396384 0 0 0 O 0.6250000000000002 0.7500000000000001 0.0781218233465462 0 0 0 O 0.6250000000000002 0.7500000000000002 0.3906091167327305 Ce 0.0000000000000000 -0.0000000000000000 0.0781218233465463 0 0 0 Ce 0.0000000000000000 -0.0000000000000000 0.2343654700396383 0 0 0 Ce 0.0000000000000001 -0.0000000000000001 0.3906091167327305 Ce 0.2500000000000002 0.2500000000000000 0.0000000000000002 0 0 0 Ce 0.2500000000000002 0.2499999999999999 0.3124872933861844 Ce 0.2500000000000002 0.2500000000000001 0.1562436466930924 0 0 0 Ce 0.5000000000000001 0.0000000000000000 0.0781218233465463 0 0 0 Ce 0.5000000000000001 0.0000000000000000 0.2343654700396384 0 0 0 Ce 0.5000000000000001 -0.0000000000000001 0.3906091167327304 Ce 0.7500000000000003 0.2500000000000001 0.0000000000000002 0 0 0 Ce 0.7500000000000003 0.2499999999999999 0.3124872933861844 Ce 0.7500000000000003 0.2500000000000001 0.1562436466930924 0 0 0 Ce 0.0000000000000000 0.5000000000000001 0.0781218233465463 0 0 0 Ce 0.0000000000000000 0.5000000000000001 0.2343654700396383 0 0 0 Ce 0.0000000000000001 0.4999999999999999 0.3906091167327304 Ce 0.2500000000000001 0.7500000000000001 0.0000000000000001 0 0 0 Ce 0.2500000000000001 0.7500000000000000 0.3124872933861844 Ce 0.2500000000000001 0.7500000000000001 0.1562436466930923 0 0 0 Ce 0.5000000000000000 0.5000000000000000 0.0781218233465463 0 0 0 Ce 0.5000000000000002 0.5000000000000001 0.2343654700396384 0 0 0 Ce 0.5000000000000002 0.5000000000000000 0.3906091167327304 Ce 0.7500000000000002 0.7500000000000001 0.0000000000000001 0 0 0 Ce 0.7500000000000002 0.7500000000000000 0.3124872933861844 Ce 0.7500000000000002 0.7500000000000001 0.1562436466930923 0 0 0 K_POINTS automatic 1 1 1 1 1 1 CELL_PARAMETERS Bohr 20.556138517348749 0.000000000000002 -0.000000000000004 0.000000000000000 14.535384940627280 0.000000000000002 -0.000000000000000 -0.000000000000000 46.515123169068765 ==================================================================== SCF in each DFGS iteration converges in about 200-300 steps. My main problem is final section of the output: ====================== . . . atom 71 type 2 force = 0.00000009 -0.00000005 -0.00000464 atom 72 type 2 force = -0.00000004 0.00000118 0.00769631 Total force = 0.000043 Total SCF correction = 0.000001 entering subroutine stress ... negative rho (up, down): 7.323E-04 7.323E-04 total stress (Ry/bohr**3) (kbar) P= -24.51 -0.00007691 0.00000000 -0.00000000 -11.31 0.00 -0.00 0.00000000 -0.00032173 0.00000000 0.00 -47.33 0.00 -0.00000000 0.00000000 -0.00010117 -0.00 0.00 -14.88 bfgs converged in 19 scf cycles and 18 bfgs steps (criteria: energy < 1.0E-09, force < 1.0E-04) End of BFGS Geometry Optimization . . ================================== As you see final stress is -24.51 kbar ??????!!!!!!!!!!!!!! As you know, for slab, we don't used "vc-relax", and only optimize ions positions. What should I do to reduce the stress on the slab? Regards David Foster Ph.D. Student of Chemistry _______________________________________________ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum