Initial Guess Keywords in the Jaguar Input File
- Overview
- Examples
Table 1 lists the keywords related to the initial guess and the meaning of the values each keyword can take on. Most of the keyword values in Table 1 correspond to options described in SCF Settings.
|
Keyword |
Value |
Description |
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0 |
No effect |
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|
1 |
Generate a spherically averaged atomic wave function for use in the |
|
0 |
No effect |
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|
|
1 |
Use initial guess or input wave function for any post-SCF calculations, skipping SCF step. No J, K, or Fock matrices are created, therefore properties that require any of these matrices cannot be calculated. |
|
0 |
Generate initial guess by diagonalizing one-electron Hamiltonian |
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|
1 |
Read initial guess from guess section from input file or from guess file specified in WAVEFNFILE line (iguess=1 automatically if input file contains non-empty guess section) |
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|
10 |
Construct initial guess from orbitals that give best overlap with atomic orbitals in |
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|
11 |
Construct initial guess from orbitals whose sum of densities best agrees with the sum of densities of the atomic orbitals in |
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|
25 |
For a system that contains transition metal atoms, construct a high-quality initial guess using ligand field theory as described in Ref. [21]. |
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|
30 |
For a system that contains transition metal atoms, construct a high-quality initial guess using ligand field theory including d-d repulsion, as described in Ref. [21]. |
|
0 |
Do not generate a new default initial guess if the original guess is bad. |
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|
1 |
Generate a new initial guess if the supplied guess is bad. The quality of the guess is determined by testing the maximum absolute value of the DIIS error vector; if it is larger than guess_thresh; a new guess is generated with the default method. |
|
1.0 |
Threshold for determining if the original guess is bad, based on the maximum absolute value of the DIIS error vector. |
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|
0 |
Construct Hamiltonian using standard orbitals |
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|
2 |
Make highest two orbitals in initial guess an open-shell singlet pair (ROHF only) |
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|
3 |
Input Hamiltonian in ham section (ihamtyp=3 by default if a non-empty ham section exists) |
|
0 |
Use the default open-shell guess. |
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|
1 |
Set up an “open-shell singlet” initial guess by mixing the LUMO into the HOMO, and set isymm=0 and iuhf=1. See text. |
|
0 |
Use the default state selection when there are degenerate states in transition-metal systems. Same as setting istate=1. |
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|
|
n |
Perform calculation on state number n. n is the index of the state in the output from hfig for degenerate states in transition-metal systems. |
|
0.01 |
For a system that contains transition metal atoms, set the energy threshold (in hartrees) when generating the set of degenerate states of possible d orbital occupations. States whose energies agree to within this threshold are considered degenerate. |
If you want to perform an “open-shell singlet” calculation using UDFT or UHF, set ioss=1. The alpha and beta HOMO are replaced with a mixture of the HOMO and LUMO, as follows:
The orbitals are taken from a closed-shell starting guess. The LUMO remains the same. This option also sets isymm=0 and iuhf=1. Do not use this keyword for transition metals, for which you should use the 2spin column in an atomic section to set up an antiferromagnetic guess.
Note: This starting guess does not correspond to the open-shell singlet state, but is a mixture of singlet closed-shell and triplet open-shell states. The final wave function in a UHF calculation will not necessarily correspond to what would be obtained in an ROHF calculation, and might be a mixture of a singlet and a triplet state. You should check the value of S2 in the output to determine the extent of spin contamination. In UDFT calculations, exchange is handled differently, and all that can be concluded is that the final density represents the lowest state. This is more correctly described as a spin-polarized method rather than an open-shell singlet method; for UDFT it yields the correct dissociation behavior for a sigma bond.
In the transition metal initial guess section (tmig), Jaguar generates a set of states with all possible d orbital occupations. You can select one of these states by setting istate to the state index. This capability is useful when there are degenerate states, such as in highly symmetric transition metal complexes. When degenerate states are encountered, Jaguar prints a warning message that lists the states with a state index number, and by default continues the calculation with the first state. By default, states are considered degenerate if they agree within 0.01 hartrees, however, this threshold can be modified using the opt325 keyword. This calculation might not converge to the ground state, so you should run calculations for each state to determine which is the desired state. To run a calculation with another state, set istate to the state index number listed in the output.