Hello, With these small residual forces I would say that your structure is well converged.
Pascal Le 16 janv. 2015 à 19:42, Anna Kuznetsova <[email protected]> a écrit : > Dear users, > > I am trying to achieve the perfect relaxation of hexagonal unit cell in > orthorhombic coordinates, however, I still see quite substantial residual > forces along z-dimension. Doing finer k-mesh sampling does not help with the > issue. > I am quite sure that the coordinates of atoms in each layer are correct, so I > was expecting that vc-relax will result only in the change in the unit cell > dimensions, but not the changes of atomic positions inside it. > > Please, give me some hints of what could be wrong in my input to help me > achieve full relaxation of the unit cell. > > > Input (also attached): > > &CONTROL > calculation = "vc-relax", > pseudo_dir = "/u/annakuz/espresso/pseudo", > outdir = "/lustre/work1/annakuz/tmp4", > / > &SYSTEM > ibrav = 8, > celldm(1) = 5.781869696282005, celldm(2) = 1.732050807568878, celldm(3) > = 1.632993161855452, > nat = 8, > ntyp = 2, > ecutwfc = 80, > ecutrho = 700, > occupations='smearing', smearing='gauss', degauss=0.03 > / > &ELECTRONS > conv_thr = 1.D-12 > / > &IONS > / > &CELL > / > ATOMIC_SPECIES > Si 28.0855 Si.pz-n-kjpaw_psl.0.1.UPF > C 12.0107 C.pz-n-kjpaw_psl.0.1.UPF > ATOMIC_POSITIONS {crystal} > Si 0.00 0.00 0.00 > C 0.00 0.00 0.375 > Si 0.50 0.50 0.00 > C 0.50 0.50 0.375 > Si 0.50 0.166666667 0.5 > C 0.50 0.166666667 0.875 > Si 1.00 0.666666667 0.5 > C 1.00 0.666666667 0.875 > > K_POINTS automatic > 15 8 9 1 1 1 > > > Output is attached but here is the final result of relaxation showing forces > still present in z-direction: > > ............ > convergence has been achieved in 31 iterations > Forces acting on atoms (Ry/au): > atom 1 type 1 force = 0.00000000 -0.00000037 0.00011491 > atom 2 type 2 force = 0.00000000 0.00000026 -0.00011491 > atom 3 type 1 force = 0.00000000 -0.00000037 0.00011493 > atom 4 type 2 force = 0.00000000 0.00000030 -0.00011491 > atom 5 type 1 force = 0.00000000 0.00000037 0.00011498 > atom 6 type 2 force = 0.00000000 -0.00000029 -0.00011498 > atom 7 type 1 force = 0.00000000 0.00000036 0.00011495 > atom 8 type 2 force = 0.00000000 -0.00000027 -0.00011497 > Total force = 0.000325 Total SCF correction = 0.000000 > > entering subroutine stress ... > total stress (Ry/bohr**3) (kbar) P= -0.09 > -0.00000088 0.00000000 0.00000000 -0.13 0.00 0.00 > 0.00000000 -0.00000088 0.00000000 0.00 -0.13 0.00 > 0.00000000 0.00000000 0.00000001 0.00 0.00 0.00 > > bfgs converged in 3 scf cycles and 2 bfgs steps > (criteria: energy < 0.10E-03, force < 0.10E-02, cell < 0.50E+00) > End of BFGS Geometry Optimization > Final enthalpy = -250.0275444323 Ry > Begin final coordinates > new unit-cell volume = 547.64431 a.u.^3 ( 81.15251 Ang^3 ) > > CELL_PARAMETERS (alat= 5.78186970) > 0.998918439 0.000000000 0.000000000 > 0.000000000 1.730177232 0.000000000 > 0.000000000 0.000000000 1.639355189 > ATOMIC_POSITIONS (crystal) > Si 0.000000000 -0.000000091 -0.000421399 > C 0.000000000 -0.000000003 0.375421398 > Si 0.500000000 0.499999909 -0.000421402 > C 0.500000000 0.499999991 0.375421397 > Si 0.500000000 0.166666758 0.499578593 > C 0.500000000 0.166666675 0.875421409 > Si 1.000000000 0.666666758 0.499578597 > C 1.000000000 0.666666671 0.875421408 > End final coordinates > > Thank you for help! > -- > Best regards, > Anna > <2h_sic_pz_vcrelax5.rx.out><2h_sic_pz_vcrelax5.rx.in>_______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
