Description of Commands

`infsao`- Command
`infsao`

provides information about the symmetry adapted basis which is used for the SCF-calculation. To exploit the molecular symmetry as efficiently as possible,`TURBOMOLE`programs do not use the simple basis which you specified during your`define`session. Instead it builds linear combinations of equal basis functions on different--but symmetry equivalent--atoms. This basis is then called the SAO-basis (**S**ymmetry**A**dapted**O**rbital). It has the useful property that each basis function transformed to this basis transforms belongs to one irreducible representation of the molecular point group (that is, the basis reflects the full molecular symmetry as specified by the Schönflies symbol).`infsao`

gives you a listing of all symmetry adapted basis functions and their constituents either on file or on the screen. This may help you if you want to have a closer look at the SCF vectors, because the vector which is output by program`dscf`is written in terms of these SAOs. `atb`-
Molecular orbitals can be written either in ASCII or in binary format.
This command switches from one option to the other, and it is highly
recommended to read which setting is currently active. ASCII format
is portable and allows the usage of
`TURBOMOLE`input files on different systems with incompatible binary format. Binary format is faster and smaller files will be written. The external program`atbandbta`

can be used to transform existing`mos`

,`alpha`

, and`beta`

files from ASCII to binary format and vice versa. `eht`-
`eht`

performs an extended Hückel calculation for your molecule. The orbital energies available from this calculation are then used to provide occupation numbers for your calculation and the Hückel MOs will be projected onto the space that is spanned by your basis set. This start-vectors are not as good as the ones which may be obtained by projection of an old SCF vector, but they are still better than the core Hamiltonian guess that is used if no start vectors are available. When using this command, you will be asked if you want to accept the standard Hückel parameters and to enter the molecular charge. Afterwards you will normally get a list of the few highest occupied and lowest unoccupied MOs, their energies and their default occupation. If you don't want to accept the default occupation you will enter the occupation number assignment menu, which is described in Section 4.3.2. Note that the occupation based on the Hückel calculation may be unreliable if the difference of the energies of the HOMO and the LUMO is less than 0.05a.u. (you will get a warning). You will also have to enter this menu for all open-shell cases other than doublets. `use`*file*- With command
`use`

you are able to use information about occupied MOs and start vectors from a former calculation on the same molecule.*file*should be the path and name of the`control`file of this former calculation, of which all data groups related to occupation numbers and vectors will be read. As the new generated data will overwrite the existing data if both resist in the same directory, it is best and in some cases necessary to have the data of the former calculation in another directory than the one you started the`define`session in. Then just type`use <path>/control`

to construct a new SCF vector from the data of the old calculation, without changing the old data. The data groups`$closed shells`and`$open shells`will be taken for your new calculation and the SCF vector from the old calculation will be projected onto the space which is spanned by your present basis set. These start vectors are usually better than the ones you could obtain by an extended Hückel calculation. `man``man`allows you to declare occupation numbers or change a previous declaration manually. After selecting this command, you will get a short information about the current occupation numbers:--------------------------------------------------------- actual closed shell orbital selection range --------------------------------------------------------- a1 # 1- 18 a2 # 1- 1 e # 1- 13 --------------------------------------------------------- any further closed-shell orbitals to declare ? DEFAULT(y)

If you answer this question with`y`, you enter the orbital specification menu which will be described in Section 4.3.3.The same procedure applies to the open-shell occupation numbers after you finished the closed-shell occupations.

`hcore`-
`hcore`

tells programs`dscf`and`ridft`to run without a start vector (it writes the data group`$scfmo none`to file`control`).`dscf`or`ridft`will then start from the core Hamiltonian start vector, which is the vector obtained by diagonalizing the one-electron Hamiltonian. Note that you still have to specify the occupation numbers. This concerns only the first SCF run, however, as for the following calculations the converged vector of the previous iteration will be taken. A SCF calculation with a core Hamiltonian start vector typically will take iterations more than a calculation with an extended Hückel start vector (a calculation with the converged SCF vector of a previous calculation will need even less iterations, depending on how large the difference in the geometry between the two calculations is). `flip`-
flipping of spins at a selected atom. Requirements: converged UHF molecular
orbitals and no symmetry (C).
`define`will localize the orbitals, assign them to the atoms and give the user the possibility to choose atoms at which alpha-orbitals are moved to beta orbitals, or vice versa. This is useful for spin-broken start orbitals, but not for spatial symmetry breaking. `*`- This command (as well as
`use`and`eht`) terminates this menu, but without providing a start vector. If the keyword`$scfmo`exists in your input file, it will be kept unchanged (i.e. the old vector will be taken), otherwise`$scfmo none`will be inserted into your output file, which forces a calculation without start vector to be performed. When you leave this menu, the data groups`$closed shells`,`$open shells`(optionally) and`$scfmo`will be written to file. You will then reach the last of the four main menus (the General Menu) which is described in Section 4.4.