---- ---- ---- ---- )))))
---- ---- ---- _ _ _ { o o }
---- ---- _(_)_(_)_ ( ^ )
---- ---- _(_)_(_)_(_)_/ /
---- ---- _(_)_(_)_(_)_(_)/
---- (_)_(_)_(_)_(_)_(_)
---- ---- ---- // // // //
an ab initio VB/VBSCF program by
J. Verbeek, J.H. Langenberg, C.P. Byrman, F. Dijkstra, J.J. Engelberts and J.H. van Lenthe
TURTLE is a program designed to perform Valence Bond Self Consistent Field (VBSCF) calculations. The method used has been developed by Van Lenthe and Balint-Kurti. It has been implemented in the TURTLE package by Verbeek.
The wavefunction can be expressed in the following way:
The wavefunction is expressed as a linear combination of structures, the coefficients are variationally optimised.
The program has the following properties :
Currently under investigation.
Currently under investigation.
Currently under investigation.
Currently under investigation.
Defines accuracy.
Defines set of active orbitals. The number of active orbitals must exceed or equal the highest occupied orbital number. The active directive couples the orbitals defined with the CONF directive in CRESTR to the basis functions or a specified set of vectors. The active directive must be followed by 'end' Example:
active 1 2 5 6 7 end
This statement couples the basisfunctions 1 2 5 6 and 7 to the functions 1 to 5 as defined in CRESTR.
Defines orbitals to be put in frozen core.
Tell TURTLE to read vectors from dumpfile or input.
Syntax:
vbvectors isec or vbvectors manual n s [print]
With isec the section of the dumpfile from wich the vectors are to be restored.
Manual tells to read the vectors from input with n vectors to read and s columns to skip per row. Print is optional; when it is used the vectors will be printed in the output. After the line with vbvector the vectors have to be given.
Example:
vbvectors manual 4 1 1 0.1000 0.3333 2 0.4444 0.1113 3 0.0000 0.0005 1 0.0000 0.0500 2 0.0000 0.1000 3 1.0000 0.6666
Currently under investigation.
Currently under investigation.
Currently under investigation.
Currently under investigation.
Currently under investigation.
The following line is read in as a title of the job.
Syntax:
iprint i
Sets printing level to i. Higher i yields more output.
Davidson shift.
Davidson (and/or) jacobi stop-criterion (and/or) orthogonality criterion.
Mix input orbitals by hand.
Maximum number of cycles in davidson.
Analyse the types of matrix elements. Not fully implemented yet.
States to select for starting vector.
Select diagonalisation mode.
Level shift alteration in Davidson.
Atom definition in terms of orbital numbers. Defines which ao's belong to which atom and which basisfunctions belong to that atom. Directive must be followed by 'end'.
Example:
mulliken c1 1 3 5 7 end 1 to 12 end c2 2 4 6 8 end 13 to 24 end end
Try to make bonding hybrids according to rumer-bonds. The hybrids are
guessed by maximising overlap.
If this directive is followed by 'AO' then per atom the AO's will be
used for it.
Clear ao's. That is remove coefficients on alien atoms. Atom definitions have to be given at the 'mulliken' option.
Reduce the number of MO's defined in the active statement.
Orthogonalise vectors using Schmidt-orthogonalisation.
Orthogonalise vectors using Lowdin-orthogonalisation.
Copy MO's just read.
Read sum of atomic energies.
Request print of CI eigenvalues and eigenvectors.
Currently under investigation.
Input finished.
Start of SCF directives
example:
scf
.....
....
end 33 {scf}
Currently under investigation.
Criterium for Jacobi, Davidson or SCF (default SCF).
Currently under investigation.
Currently under investigation.
Currently under investigation.
Perform level shift in SCF.
The ortho directive allows one to switch off the allowed orthogonalisations; By default for instance singly occupied are orthogonalised to the doubly occupied ones. Note that the VBCI does not do these orthogonalitiations
example :
ortho off
Currently under investigation.
Define atoms for automatic atom-scf procedure.
Syntax:
hybrids atom functions end basisfunctions end end
Example:
hybrids c1 1 3 5 7 end 1 to 12 end c2 2 4 6 8 end 13 to 24 end end
Force orbitals to be equivalent.
Do not use the symmetry.
Do not use symmetry due to spin in matrix element evaluation.
Do not allow internal excitations. These are replaced by excitations to ao's.
Currently under investigation.
Treat excitations by perturbation theory.
pert idelp itp shiftp
start perturbation treatment of virtuals after del < idelp and iteration itp use a level shift of shiftp for the perturbation part.
Optimize orbitals for excited state.