# Input description¶

## Relevant Keywords in QUILD block¶

 name default description CVG_ENR 1.0e-5 Convergence criterium for energy (when IDCVG $$\geq$$ 2) CVG_GRD 1.0e-4 Convergence criterium for maximum component of gradient; depending on the value of IDELOCAL, either the delocalized or Cartesian gradient is checked CVG_STP 1.0e-4 Convergence criterium for maximum component of step (when IDCVG $$\geq$$ 2) DIFSTEP 1.0e-5 Stepsize for numerical differentiation (with numerical gradients/Hessian)) I_ADD_DUMMIES 1 Index to do (1) or do not (0) add dummy atoms for avoiding (nearly-)linear angles ICREATE 7 Index which method to use for generating the primitive coordinates IDCVG 1 Index how to signal convergence: 1. check nr. of negative Hessian eigenvalues is correct and max. component and rms value of gradient are less than the convergence criterium (see CVG_GRD) 3. same as 1, but both max. component of step and change in energy should be less than their respective convergence criteria (see CVG_STP and CVG_ENR) 2. same as 3, but only of the additional criteria has to be fulfilled IDELOCAL 1 Kind of coordinates to use in the geometry optimization: 1. adapted delocalized coordinates 0. Cartesian coordinates IDIIS 3 Kind of GDIIS equations to use: 0. original GDIIS 1. same as 0, but with Farkas-Schlegel rules applied 2. use gradient as error vector 3. same as 2, but with Farkas-Schlegel rules applied 4. use ‘energy’ vector as error vector 5. same as 4, but with Farkas-Schlegel rules applied IDSTEP 5 Step to take: 1. RSO for minimizations, RFO (Baker) for TransitionStates 3. RFO (Baker) always 5. Generalized RSO (Swart) using image-function for TransitionStates IEXCST 1 Number of excited state to use for numerical gradients By default for singlet excited state; triplet excited state can be used by adding ONLYTRIP keyword to EXCITATIONS block on input IHOPT 3 Index for force constants method to use for initial Hessian: 0. Baker (0.5 bonds, 0.2 angles, 0.1 dihedrals) 1. Thomas Fischer 2. simplification of Lindh 3. Swart-Bickelhaupt scheme 7. Swart generalized scheme (works well for close to minima) IHUPD -1 cq. 4 Index for Hessian update scheme: 1. BFGS for Hessian (-1 BFGS for inverse Hessian) 2. Powell-symmetric-Broyden, PSB (for Transition States) 3. Murtagh-Sargent (Symmetric Rank-One, SR1) 4. Bofill weighted combi of PSB and SR1 (for Transition State) 5. Farkas-Schlegel weighted combi of BFGS and SR1 6. Bakken-Halgaker combi of BFGS and SR1 IQUILD_OUTPUT 1 Amount of output requested, debug output $$\geq$$ 2 IRESTART 0 Index if ADF/ORCA jobs should restart from t21.files from previous geometry < 0 ORCA uses restart, ADF not > 0 both ORCA and ADF use restart ITRUST 0 Index if dynamic trust radius should be used (1) or not (0) MXDIIS 5 Maximum number of GDIIS vectors to use MXGEO 50 Maximum number of geometry cycles (overrides value read from ITERATIONS in GEOMETRY block) NR_REGIONS 1 Number of different regions for multi-level approach NRLT 0 Number of LinearTransit steps RTRUST 0.20 Trust radius value SMETAGGA String for functional from METAGGA post-SCF scheme to use for numerical gradients, should be given exactly as on METAGGA output TRUST_ALFA 1.20 Factor to increase trust radius with if $$\Delta$$ energy agrees with model prediction TRUST_BETA 0.70 Factor to decrease trust radius with if $$\Delta$$ energy does not agree with model TRUST_GOOD 0.80 Lower threshold for increasing trust radius TRUST_RMIN 0.40 Upper threshold for increasing trust radius

The other keywords that are printed in the output are for debug purposes, under development, or of technical nature. More information about them can be obtained (if needed) from SCM or M. Swart.

## CONSTR subblock in QUILD block¶

Constraints can be supplied in the CONSTR subblock of QUILD. Below are the different option that are possible:

QUILD
CONSTR
dist   1 2         0.9
angle  1 2 3     120.0
dihed  1 2 3 4   100.0
x      1           0.0   ! only with idelocal=0
y      1           0.0   ! only with idelocal=0
z      1           0.0   ! only with idelocal=0
SUBEND
END


The units of these constraints are determined by the parameters in the UNITS block. The numbers in this subblock refer like usual to the atom numbers, as they are found in the ATOMS block.

A special case is observed for LinearTransit calculations, as given in the example below.

QUILD
nrlt 11
CONSTR
dist   1 2         1.0    2.0
angle  1 2 3     120.0   70.0
SUBEND
END


Here there are two LinearTransit coordinates, i.e. the distance between atoms 1 and 2 and the angle 1-2-3. The distance between atoms 1 and 4 is a simple constraint throughout the whole calculation.

## FROZEN subblock in QUILD block¶

Another way to introduce constraints is by freezing certain atoms. This can be achieved with the FROZEN subblock of QUILD, where either all three Cartesian (x, y, z) coordinates of an atom (or a series of atoms) can be frozen, or only one of the three:

QUILD
FROZEN
x      1-37   ! the X-coordinates of atoms 1 to 37 are kept frozen
xyz   48-256  ! the X,Y,Z-coordinates of atoms 48 to 256 are kept frozen
SUBEND
END


## SYMROT subblock in QUILD block¶

Sometimes, one wants to lower the symmetry because of more convenient descriptions of d-orbitals of transition metals for instance. In that case, if one still wants to maintain the higher symmetry for the geometry, one can use the SYMROT subblock to rotate the coordinates. For instance, for Fe(II)(Cl)4 2- with Td geometric symmetry, the Fe d-orbitals are not conveniently separated. This might be better done within C2v symmetry:

Symmetry C(2v)

QUILD
Symgeo T(d)
Symrot
-0.7071067811865475 -0.7071067811865475  0.0
-0.7071067811865475  0.7071067811865475  0.0
0.0                 0.0                 1.0
Subend
End

Atoms
Fe               0.000000000    0.000000000    0.000000000
Cl              -1.326583289    1.326583289    1.326583289
Cl              -1.326583289   -1.326583289   -1.326583289
Cl               1.326583289    1.326583289   -1.326583289
Cl               1.326583289   -1.326583289    1.326583289
End


This transforms the coordinates from Td symmetry:

Atomic coordinates

atom       nr    x (Bohrs)   y (Bohrs)   z (Bohrs)       x (angs)    y (angs)    z (angs)
--------------------------------------------------------------------------------------------
FE          1      0.00000     0.00000     0.00000        0.00000     0.00000     0.00000
CL          2     -2.50688     2.50688     2.50688       -1.32658     1.32658     1.32658
CL          3     -2.50688    -2.50688    -2.50688       -1.32658    -1.32658    -1.32658
CL          4      2.50688     2.50688    -2.50688        1.32658     1.32658    -1.32658
CL          5      2.50688    -2.50688     2.50688        1.32658    -1.32658     1.32658


to C2v symmetry:

SYMMETRY C(2V)
Atoms
FE               0.000000000    0.000000000    0.000000000
CL               0.000000000    1.876072079    1.326583289
CL               1.876072079    0.000000000   -1.326583289
CL              -1.876072079    0.000000000   -1.326583289
CL               0.000000000   -1.876072079    1.326583289
End


The particular rotation matrix to be used depends on the choice made by the user for how to represent the molecule in the lower symmetry (see ADFinput how to impose symmetry).

## TSRC subblock in QUILD block¶

The Transition State Reaction Coordinates that are used to construct the special initial Hessian, should be given in the TSRC subblock of QUILD. Similar to the CONSTR subblock, the distances, angles, or dihedrals should be specified, one per line, with atom numbers. The atom numbers should refer to the atoms as they are found in the ATOMS block.

QUILD
TSRC
dist   1 2
angle  1 2 3
dihed  1 2 3 4
SUBEND
END


## REGION subblocks in QUILD block¶

The definition of the different regions should be given in REGION subblocks of QUILD. Although the program counts the number of regions itself, it should be regarded good practice to make sure that the NR_REGIONS keyword corresponds to the correct number of REGION subblocks.

QUILD
NR_REGIONS 2
REGION 1
1-11
SUBEND
REGION 2
12 14 13 15 16 17 19 18 22 21 20
SUBEND
END


The order in which the atom numbers are given does not matter, and in order that the input is easier to make and read, shortcuts are introduced. For instance, the “1-11” shortcut corresponds to “1 2 3 4 5 6 7 8 9 10 11” etc. Unlike other multi-level approaches, there is no need to have a shell structure for the different regions. I.e., the regions can overlap, or be defined as given above for DNA.

## ADDREMOVE subblock in QUILD block¶

There is no ADDREMOVE subblock of QUILD active yet, but in the future it will be added to be able to control how the capping atoms will be added in the case of regions with dangling bonds. I.e., which elements should be added, and so on. For the moment, only hydrogens will be added, which works without problems for QM/QM and/or QM/MM calculations on DNA, or simple peptides. Future developments should decide whether this needs to be adapted.

## DESCRIPTION subblocks in QUILD block¶

In case of multi-level jobs, where different regions are treated with different methodologies, the different methodologies should be given in the DESCRIPTION subblocks.

QUILD
XC
GGA OPBE
END
BASIS
type TZ2P
core NONE
END
SUBEND
XC
HYBRID B3LYP
END
basis
type DZ
core NONE
end
SUBEND
DESCRIPTION 3 ORCA NUMFREQ
%method method hf