CO
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Task
Relaxation of the bond length in a CO molecule.
Input
POSCAR
CO molecule in a box 1.0 ! universal scaling parameters 8.0 0.0 0.0 ! lattice vector a(1) 0.0 8.0 0.0 ! lattice vector a(2) 0.0 0.0 8.0 ! lattice vector a(3) 1 1 ! number of atoms for each species cart ! positions in cartesian coordinates 0 0 0 ! first atom 0 0 1.12 ! second atom
INCAR
SYSTEM = CO molecule in a box ISMEAR = 0 ! Gaussian smearing NSW = 5 ! 5 ionic steps IBRION = 2 ! use the conjugate gradient algorithm
KPOINTS
Gamma-point only 0 Monkhorst Pack 1 1 1 0 0 0
POTCAR
The POTCAR file is created by the concatenation of two individual POTCAR files corresponding to O and C, e.g.:
cat .../O/POTCAR .../C POTCAR > POTCAR
Calculation
- A similar relaxation as in the previous case (O_dimer) is performed but in this case more steps are required, since the first estimate for the minimum is not very accurate. The trial steps are much too long (POTIM parameter).
1 F= -.14764064E+02 E0= -.14764064E+02 d E =-.147641E+02 curvature: 0.00 expect dE= 0.000E+00 dE for cont linesearch 0.000E+00 trial: gam= 0.00000 g(F)= 0.820E+00 g(S)= 0.000E+00 ort = 0.000E+00 (trialstep = 0.100E+01) search vector abs. value= 0.820E+00 bond charge predicted ... ... ... ... ... ... ... ... ... 2 F= -.12660858E+02 E0= -.12660858E+02 d E =0.210321E+01 trial-energy change: 2.103205 1 .order 1.311207 -0.819873 3.442288 step: 0.1924(harm= 0.1924) dis= 0.02705 next Energy= -14.842919 (dE=-0.789E-01) bond charge predicted ... ... ... ... ... ... ... ... ... 3 F= -.14747869E+02 E0= -.14747869E+02 d E =0.161943E-01 curvature: -0.10 expect dE=-0.902E-01 dE for cont linesearch -0.902E-01 ZBRENT: interpolating opt : 0.0929 next Energy= -14.802162 (dE=-0.381E-01) bond charge predicted ... ... ... ... ... ... ... ... ... 4 F= -.14796822E+02 E0= -.14796822E+02 d E =-.327586E-01 curvature: -0.04 expect dE=-0.330E-03 dE for cont linesearch -0.330E-03 trial: gam= 0.00000 g(F)= 0.814E-02 g(S)= 0.000E+00 ort =-0.817E-01 (trialstep = 0.819E+00) search vector abs. value= 0.814E-02 reached required accuracy - stopping structural energy minimisation