CASINO manual - Theory of Condensed Matter
CASINO manual - Theory of Condensed Matter
CASINO manual - Theory of Condensed Matter
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% mv Test.FChk dna.Fchk<br />
run gaussiantoqmc . . . and follow the prompts<br />
% mv dna.qmc gwfn.data<br />
run casino.<br />
The code should automatically detect what sort <strong>of</strong> gaussian job it is and give you the opportunity<br />
to construct an excited-state wave function if applicable.<br />
It can deal with the following sorts <strong>of</strong> calculation:<br />
• HF and DFT ground states, open and closed shell.<br />
• CIS excited states, open and closed shell.<br />
• CASSCF states. Getting gaussian to output these can be problematic for large calculations.<br />
It is possible that gaussiantoqmc will get confused if you use some combination <strong>of</strong> IOps other<br />
than those described in Sec. 8.6.3.<br />
• Time-dependent HF (TD-HF) or DFT (TD-DFT) excited states.<br />
If the user chooses to output a CIS or TD-DFT wave function, they are given the option <strong>of</strong> resumming<br />
it. The wave function must also be resummed if the user wishes to analyse its composition. As<br />
distributed, gaussiantoqmc will not do this analysis but if you wish to switch this option on then the<br />
flag analyse cis in cis data.f90 must be set to T and gaussiantoqmc recompiled.<br />
With this flag set the code evaluates the percentage contribution <strong>of</strong> each single excitation to the CIS<br />
expansion. Degenerate virtual and occupied orbitals are identified and their contributions summed.<br />
The final output takes the form <strong>of</strong> files called fromi j.dat where i–j indicates a range <strong>of</strong> degenerate<br />
occupied orbitals (if i = j then i is a nondegenerate orbital). These files detail all excitations out<br />
<strong>of</strong> the specified orbitals along with a percentage giving their contribution to the CIS expansion as a<br />
whole. The sum <strong>of</strong> the percentages (final column) from each <strong>of</strong> the fromi j.dat should be 100 if<br />
everything is working OK.<br />
8.6.2 Other features <strong>of</strong> GAUSSIANTOQMC<br />
The code also contains some crude normalization and plotting routines that are really just debugging<br />
aids. By setting the flag test=T in gaussiantoqmc.f90 and recompiling, the user is given the option<br />
<strong>of</strong> plotting and testing the normalization <strong>of</strong> individual molecular orbitals. The axis along which the<br />
plotting is done is set in wfn construct.f90 and this must be hacked if the user wishes to change<br />
things.<br />
8.6.3 Getting GAUSSIAN to do what you want<br />
In principle, gaussian can do an awful lot <strong>of</strong> things. In fact, some <strong>of</strong> these things seem to require<br />
magical incantations. These will be described in this section, broken down into the different calculations<br />
to which they apply. The comments on g98 refer to revision A9 and may depend on which<br />
version is used.<br />
General bits and pieces<br />
Some points to note:<br />
• Both g94 and g98 appear to have formatting errors when printing out the Gaussians used in<br />
the ECP expansion—large exponent values are replaced with stars. This does not affect the<br />
subsequent calculation.<br />
• g94’s ECP (pseudopotential) package will not accept expansions containing more than 13 Gaussians<br />
per angular-momentum channel.<br />
• g98’s ECP integral package crashes when one attempts to do a large (both in terms <strong>of</strong> basis<br />
and ECP expansion) calculation with symmetry switched on. The solution to this is to switch<br />
symmetry <strong>of</strong>f using ‘Nosymm’.<br />
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