Dear all, I'm proceeding with a vc-relax calculation with conv_thr = 10-6 ; energy and force default values. The pressure goes to zero but at the last structure the pressure increases to ~ -8 kbar. Since the pressure is negative one must think that the cell is expanding, but what it is observed (checking the cell parameters) is that the cell is contracting.Why is this happening? Thank you in advance, Dr. Inna NangoiGrupo de Físico-Química de Sólidos e Interfaces (GFQSI)http://www.ufjf.br/gfqsi/Universidade Federal de Juiz de Fora - UFJF
INPUT: / &SYSTEM ibrav = 0, celldm(1) = 1.8897265, nat = 408, ntyp = 2, ecutwfc = 40 , ecutrho = 400 , / &ELECTRONS conv_thr = 1.D-6 , / &IONS / &CELL /CELL_PARAMETERS cubic 16.467196779 0.003155548 0.004141842 0.003137055 16.453425288 -0.000761157 0.004171643 -0.000775474 16.446571996ATOMIC_SPECIES O 16.00000 O.pbe-n-kjpaw_psl.1.0.0.UPF H 1.01000 H.pbe-kjpaw_psl.1.0.0.UPFATOMIC_POSITIONS angstromO 9.321137481 14.266560377 9.327818241H 9.682105309 14.676153052 8.481823531H 10.049781829 14.333756337 10.015860139O 11.166283791 6.044399971 2.975926238.. . K_POINTS gamma OUTPUT: End of BFGS Geometry Optimization Final enthalpy = -5995.1370960771 RyBegin final coordinates new unit-cell volume = 28794.22023 a.u.^3 ( 4266.86316 Ang^3 ) density = 0.95375 g/cm^3 CELL_PARAMETERS (alat= 1.88972650) 16.229014053 0.002449560 0.005745845 0.002429308 16.219588894 0.000479082 0.005772101 0.000461059 16.209758644 ATOMIC_POSITIONS (angstrom)O 9.180431407 14.143089383 9.191719262H 9.561522937 14.567241497 8.352842759H 9.908913197 14.170313644 9.891402550O 11.026600724 5.996092777 2.933422632H 11.877618746 6.446014321 2.622523705H 10.719968316 6.437111173 3.792164500O 5.141235135 15.134646177 1.987199104H 4.933636936 15.342422258 1.017207703H 5.853001846 14.414601411 1.987420436 . . . H 13.338033020 5.155154854 13.251553812O 11.079195321 9.183121298 6.146092164H 10.379755422 9.912994593 6.143398011H 11.912644022 9.559263869 5.711046728End final coordinates . . . Total force = 0.008044 Total SCF correction = 0.000070 Computing stress (Cartesian axis) and pressure negative rho (up, down): 9.616E-06 0.000E+00 total stress (Ry/bohr**3) (kbar) P= -8.32 -0.00005717 -0.00000010 -0.00000025 -8.41 -0.01 -0.04 -0.00000010 -0.00005654 0.00000006 -0.01 -8.32 0.01 -0.00000025 0.00000006 -0.00005604 -0.04 0.01 -8.24 total stress (Ry/bohr**3) (kbar) P= -12.00 total stress (Ry/bohr**3) (kbar) P= -10.74 total stress (Ry/bohr**3) (kbar) P= -7.11 total stress (Ry/bohr**3) (kbar) P= -2.92 total stress (Ry/bohr**3) (kbar) P= 0.65 total stress (Ry/bohr**3) (kbar) P= 0.70 total stress (Ry/bohr**3) (kbar) P= 0.30 total stress (Ry/bohr**3) (kbar) P= 0.08 total stress (Ry/bohr**3) (kbar) P= -0.19 total stress (Ry/bohr**3) (kbar) P= -0.43 total stress (Ry/bohr**3) (kbar) P= -0.58 total stress (Ry/bohr**3) (kbar) P= -0.40 total stress (Ry/bohr**3) (kbar) P= -0.06 total stress (Ry/bohr**3) (kbar) P= 0.25 total stress (Ry/bohr**3) (kbar) P= 0.42 total stress (Ry/bohr**3) (kbar) P= 0.43 total stress (Ry/bohr**3) (kbar) P= 0.26 total stress (Ry/bohr**3) (kbar) P= -0.03 total stress (Ry/bohr**3) (kbar) P= -0.29 total stress (Ry/bohr**3) (kbar) P= -0.53 total stress (Ry/bohr**3) (kbar) P= -0.37 total stress (Ry/bohr**3) (kbar) P= -0.19 total stress (Ry/bohr**3) (kbar) P= 0.18 total stress (Ry/bohr**3) (kbar) P= 0.36 total stress (Ry/bohr**3) (kbar) P= 0.50 total stress (Ry/bohr**3) (kbar) P= 0.33 total stress (Ry/bohr**3) (kbar) P= 0.06 total stress (Ry/bohr**3) (kbar) P= -0.09 total stress (Ry/bohr**3) (kbar) P= -0.34 total stress (Ry/bohr**3) (kbar) P= -0.28 total stress (Ry/bohr**3) (kbar) P= -0.10 total stress (Ry/bohr**3) (kbar) P= 0.03 total stress (Ry/bohr**3) (kbar) P= 0.25 total stress (Ry/bohr**3) (kbar) P= 0.25 total stress (Ry/bohr**3) (kbar) P= -8.32
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