scfguess
This option defines the initial guess of SCF calculations.
type
Value | hcore Will use the eigenvectors of the core matrix as initial guess. Usually, its performance is very bad |
atmden Will use the superposition of converged densities of all atoms in the system as initial guess. It is recommended for most cases |
|
fragden Will use the superposition of converged densities of fragments assigned by you as initial guess. This can be used for using TSO or treating symmetry-broken systems |
|
mwfn Will read a wave function from a MWFN file as initial guess |
|
Default | atmden |
Define the type of initial guess. In most cases, atmden
is recommended. mwfn
which reads a guess from a converged SCF is also a good choice.
For target state optimization (TSO), symmetry-broken, or other special calculations, fragden
can be used.
file
Value | A file name |
Default | job name + .mwfn |
Assign the mwfn file name when type
is mwfn
. Qbics will read wave function from this file.
frag
This defines atomic fragments for initial guess. The format is:
frag num_electrons spin_multiplicity atom_range
There can be arbitrary number of fragments, but all atoms must be included once and only once. They are only activated when type
is fragden
.
For example:
scfguess
type fragden
frag 0 1 1-9
frag 0 -3 10-15 18
frag -1 3 16 17
end
In this case, the molecule is decomposed into 3 fragments: (1) atom 1,2,3,4,5,6,7,8,9, with charge 0 and spin multiplicity 1; (2) atom 10,11,12,13,14,15,18, with charge 0 and spin multiplicity 3 (beta orbitals occupied first); (3) atom 16,17, with charge -1 and spin multiplicity 3.
For this guess, Qbics will perform 3 SCF calculations for all fragments, then superpose them as the initial guess for the SCF of the whole molecule. This can be used for ordinary, symmetry-broken, or TSO SCF.
The total charge of fragments does not have to be the same as the total system.
Please refer to the keyword do_tso
in scf for more details about TSO, when you want to use frag
.
orb
This defines the orbitals for initial guess. The format is:
orb num_electrons spin_multiplicity alpha_MO_indices : beta_MO_indices
There can be arbitrary number of orbital spaces, but all orbitals must be included once and only once. They are only activated when type
is mwfn
.
For example:
scfguess
type mwfn
file x.mwfn
orb 12 1 1-6 : 1-6
orb 2 1 7 : 8
orb 0 1 8 : 7
end
In this case, the orbitals will be read from x.mwfn
and 3 orbital spaces are defined: (1) alpha orbital 1,2,3,4,5,6 and beta orbital 1,2,3,4,5,6, with 12 electron and spin multiplicity 1; (2) alpha orbital 7 and beta orbital 8, with 2 electrons and spin multiplicity 1; (3) alpha orbital 8 and beta orbital 7 with 0 electron and spin multiplicity 1 (since no electrons in this orbital space, actually spin multiplicity can be arbitrary).
For this guess, Qbics will read orbitals from x.mwfn
and assign occupation according to orb
, then do the following ordinary or TSO SCF calculations.
Also, note that in this keyword, orbital order matters. For example,
scfguess
type mwfn
file x.mwfn
orb 14 1 1-6 9 7 8 10-25 : 1-6 9 7 8 10-25
end
In this case, the 7 alpha and 7 beta electrons will occupy orbital 1,2,3,4,5,6,9.
Please refer to the keyword do_tso
in scf for more details about TSO, when you want to use orb
.