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The default units for the run phase section are Ry for energies and bohr for distances.

Current constraints, important version notes:

- geometry section only at end of run phase section before v2.53
- geometry input ends with "
`end geometry`" as of v2.53 - cell optimization installed in v2.53

The following are the common input keywords in this section.
All the keywords are optional, and can appear in any order within this section.
The keywords must be left-justified, but all data input is free-format.
`
`

**run phase data**- begin run phase data input section- ...
**temperature (Ry) for occupation weighting***temp***blend ratio**- initial scf blend factor*blend*(require 0 <*blend*< 1)**scfbl2**- scf blend factor for subsequent geometries in relaxation*scfbl2*(require 0 <*scfbl2*< 1)**convergence**- scf convergence criterion (Ry) (delta-Hamiltonian matrix)*conv_scf***states**- number of eigenstates to obtain in solve*n_state***iterations**- maximum number of scf iterations*n_iter***history**- max number scf iterations in Broyden blend history*n_hist_scf***no ges**- turns off dynamic SCF guessing, reverts to overlapping spherical atom guess (2.61)**cutgrd**- set orbital range on grid, see explanation below*cutgrd*Default=2d-8 (2.65), 2d-7 (2.64 and earlier)**cutfrc**- alter force integral cutoffs*cutfrc*(set to 0.01 - 0.001 for fine stress accuracy)**cutfac**- alter all integral cutoffs*cutfac*(less accurate 10.0 - 1.0 - 0.001 most accurate)**closed shell**- enforce closed shell (0K w/gap) occupations (2.59)**kclosed shell**- almost closed shell, finite T within k-pt (2.59)- ...
**spconv**- set convergence for spin polarization (in electron #)*conv_sp***spmeth**- method for spin optimization*method_sp*(a6) (method_sp = SIMPLE, LINEAR=default )**spsteps**- number of steps (trial polarizations) to find optimal spin*nstep_sp***spblend**- blend factor for spin update (simple scheme)*blend_sp*(should be between 1.0-2.0, default=1.5, "safe"=1.0)- ...
**dynamics**- invokes MD input section- ...
*MD data input* - end dynamics - end of MD input section
- ...
**geometry relaxation**- invokes geometry input section- ...
*geometry optimization data* - end geometry - end of geometry input section
- ...
**cell optimization**- invokes cell input section- ...
*cell optimization data* - end cell parameters - end of cell optimization input section
- ...
**bandstructure**- invokes band structure input section- ...
*band structure configure* - end bands - end of band structure configure section
- ...
**end run phase data**- end of run phase input section

The criterion the code uses to determine convergence is a change (Ry) in any matrix element. In every SCF cycle, the Broyden code writes out what the rms and max change are (grep output for 'scfch', or 'max change' for pre-2.63). For different problems, metals vs. insulators, transition metals vs. alkali metals, etc., the convergence of the energy (and other properties) will be different as a function of the convergence criterion. The user can examine this relative convergence, and modify the SCF criterion appropriately to either converge more finely (make the criterion smaller) or to converge less if the problem is overconverged for their needs (make the criterion larger).

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- If it fails to converge in the first step ...
- Check that atomic configuration makes sense
- e.g.: scaling set to convert Angstrom to bohr, correct cell dimensions
- Check that atomic identities are correct in setup phase
- e.g.: that you have not accidentally interchanged hydrogen atoms and carbon atoms to create a carbohydrogen
- Change the initial
**blend ratio** - The default is 0.30. Try smaller, to as small as 0.01, or bigger, to as big as 0.80
- If the calculation is still converging (according to "max change"),
increase the maximum
**iterations** - If "max change" is still shrinking (not stalled), sometimes you just need more iterations to converge the calculation
- If metallic (no gap), esp. transition metal, try increasing the
electronic
**temperature**. - The default is 0.003 Ry. Maybe a higher temperature, 0.010 or even 0.020 will stabilize the calculation? The energies, forces, and stresses are not as good, but this is a common means to stabilize the SCF in a difficult metal.
- Change (increase) the
**convergence**parameter - If the SCF stalls but is reasonably well converged, this works. Examine total energy vs. "max change" as a function of iterations in the output file ("max change" is the figure of merit for SCF)
- Reduce the
**history**used in the Broyden SCF blend - "Forget" bad iterations more quickly by reducing the used history (to as small as 4 or 5 perhaps)
- If a metal (esp. a free-electron metal like aluminum), check that you
have sufficient
**states**specified. - Look in the output file in the eigenstate/occupation listing. If the highest state (in any k-point) is occupied, you may not have solved for enough states. Increase the number of states until you have at least one (and preferably more) empty states at the top.

- If the SCF succeeds in the first step, and fails after that ...
- Change the SCF blend parameter for follow-on steps ("
**scfbl2**") - With SCF guessing ON, the follow-on steps may have a different SCF behavior.
- Turn off the SCF guessing scheme ("
**no ges**") -
Sometimes the SCF guess goes bad.
There is a known problem (bug) with the SCF guess if an atom crosses
a boundary of the principal unit cell in a relaxation/MD when
using non-gamma k-points.
The
**no ges**option turns the guessing off. - Take the last good geometry and restart the calculation
- As mentioned above, the SCF guess will go bad in a non-gamma point calculation if an atom crosses a cell boundary. If you simply take that last geometry and relaunch a new calculation (which will start without a SCF guess), that geometry will converge.

- Change the SCF blend parameter for follow-on steps ("