#! /bin/sh


# One can run into SCF convergence problems when calculating certain types of
# systems. Some of the notorious examples are transition metal oxides and
# lanthanide compounds. Below, several approaches to solving the SCF convergence
# problem are demonstrated.


AMS_JOBNAME=Default $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (default case)
  basis
    core Small
    type DZ
  end
  scf
    converge 1.0e-6 1.0e-6
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor


AMS_JOBNAME=MESA $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test MESA
  basis
    core Small
    type DZ
  end
  scf
    accelerationmethod MESA
    converge 1.0e-6 1.0e-6
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor


AMS_JOBNAME=LISTb $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (LISTb by Alex Wang)
  basis
    core Small
    type DZ
  end
  scf
    accelerationmethod LISTb
    converge 1.0e-6 1.0e-6
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor


AMS_JOBNAME=LISTf $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (LISTf by Alex Wang)
  basis
    core Small
    type DZ
  end
  scf
    accelerationmethod LISTf
    converge 1.0e-6 1.0e-6
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor


AMS_JOBNAME=fDIIS $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (fDIIS by Alex Wang)
  basis
    core Small
    type DZ
  end
  scf
    accelerationmethod fDIIS
    converge 1.0e-6 1.0e-6
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor



# A-DIIS method. The A-DIIS method combines the strength of the ARH and DIIS
# methods. It does not require energy evaluation so it is much cheaper than the
# ARH and Energy-DIIS methods.


AMS_JOBNAME=ADIIS $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (A-DIIS by Hu and Yang)
  basis
    core Small
    type DZ
  end
  occupations KeepOrbitals=100
  scf
    accelerationmethod ADIIS
    converge 1.0e-6 1.0e-6
    iterations 300
    mixing 0.05
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor



# This example uses the LISTi method. LISTi is very
# similar to the usual DIIS but typically it performs much better. It is also
# computationally less expensive and scales better in parallel even though DIIS
# is rarely a scaling bottleneck. 


AMS_JOBNAME=LISTi $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (LISTi)
  basis
    core Small
    type DZ
  end
  scf
    accelerationmethod LISTi
    iterations 300
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor



# This example uses the Augmented Roothaan-Hall (ARH) method. 
# The basic idea of this method is that the density matrix is
# optimized directly to minimize the total energy. Important: the ARH method can
# be used with SYMMETRY NOSYM only. 


AMS_JOBNAME=ARH $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (Augmented Roothaan-Hall)
  basis
    core Small
    type DZ
  end
  scf
    arh
    end
    iterations 300
    mixing 0.05
  end
  symmetry NOSYM
  xc
    gga Becke Perdew
  end
EndEngine
eor



# This is an extension to the so-called 'electron smearing' method.
# In this method, the electrons are distributed among orbitals around Fermi-
# level using a pseudo-thermal distribution function. Although the result with
# fractional occupation number has no physical sense, the method can be used to
# achieve integer occupation numbers by reducing the smearing parameter step-
# wise. 
# A few notes:

# You can specify up to ten comma-delimited values after Smear= (no spaces are
# allowed). ADF will start from the first value and try to converge SCF using
# it. If it succeeds, the next value will be picked and so on.

# Because the whole process may require many cycles to converge it is important
# to set the number of SCF cycles to a large value to avoid a premature
# termination.


AMS_JOBNAME=Smear $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (Smear)
  debug DIIS SDIIS
  basis
    core Small
    type DZ
  end
  occupations Smear=0.2,0.1,0.07,0.05,0.03,0.02,0.01,0.007,0.005,0.001
  scf
    iterations 300
    oldscf
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor


# This example demonstrates the use of the Occupations Steep= option (see
# the User's Guide for details). 

# One difference is, obviously, in the Occupations keyword. The other difference
# is more subtle. For stable convergence, it is often essential to switch off
# DIIS and set the mixing parameter to a low value. Of course, it will make
# convergence quite (sometimes very) slow. Ultimately you should get either an
# aufbau configuration or a configuration with exactly degenerate HOMO. In this
# example, the result is an aufbau solution.

# Both methods should, in principle, give the same result, which is the case in
# this example.


AMS_JOBNAME=Steep $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (Steep)
  basis
    core Small
    type DZ
  end
  occupations Steep=0.5,0.3
  scf
    diis
      n 0
    end
    iterations 300
    mixing 0.05
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor


# This example uses the so called Energy-DIIS method. Please note that similar
# to ARH and unlike the standard SCF procedure in ADF this method requires
# energy evaluation at each SCF cycle, which makes it significantly slower
# compared to energy-free SCF.


AMS_JOBNAME=EDIIS $AMSBIN/ams <<eor
System
  atoms
     Ti  1.730   0.000   0.000
     Ti -1.730   0.000   0.000
     O   0.000   1.224   0.000
     O   0.000  -1.224   0.000
     O   3.850   0.000   0.000
     O  -3.850   0.000   0.000
  end
end

Task SinglePoint

Engine ADF
  title Ti2O4 SCF aid test (Energy-DIIS)
  basis
    core Small
    type DZ
  end
  scf
    converge 1.0e-6 1.0e-6
    ediis
    iterations 300
    mixing 0.05
  end
  xc
    gga Becke Perdew
  end
EndEngine
eor