CASINO manual - Theory of Condensed Matter

CHECKPOINT NCPU (Integer) This keyword can be used to specify how to group CPUs for
reading config.in checkpoint files. Having many CPUs access the same file at the same time
is not a good idea; therefore we form groups of checkpoint ncpu cores in which only one of
them accesses data. The default value is the total number of cores (nnodes internally), but
depending on the hardware you run on you may want to set checkpoint ncpu to a different
value (between 1 and nnodes). Note that in the case that nnodes is not exactly divisible by
checkpoint ncpu, then the remainder will be distributed over the existing groups, and some
of the groups will therefore contain checkpoint ncpu+1 cores.
CHECKWFN (Logical) Enable a numerical check of the analytic orbital derivatives coded in the
various routines such as gauss per/gauss mol/bwfdet/pwfdet, etc. This is primarily intended
to help developers ensure that they have coded up the analytical derivatives of new forms of
wave function correctly.
COMPLEX WF (Logical) If complex wf is set to T then a complex Slater wave function will be
used. The orbital-evaluation routines will not attempt to construct real orbitals by forming linear
combinations of complex orbitals. It is necessary to set complex wf to T in periodic calculations
if twisted boundary conditions are to be applied or if twist averaging is to be performed. Note
that complex arithmetic is somewhat slower than real arithmetic and hence complex wf should
be set to F wherever possible. Information about the use of twisted boundary conditions can be
found in Sec. 28.
CON LOC (Character) The config.out and config.in configuration-data files are written to and
read from the directory specified by con loc. By default con loc is the directory in which
casino is run.
COND FRACTION (Logical) If cond fraction is set to T, then an improved estimator of the
spherically averaged two-particle density matrix, from which one-body contributions are subtracted,
will be computed. This is currently only available if the system is homogeneous.
CONTACT DEN (Logical) If this flag is set then casino will accumulate the spatial overlap between
electrons and a positron. At present this is only relevant in studies of positronic molecules.
CONV BINARY BLIPS (Logical) In November 2011, a new format binary blip file
bwfn.data.bin was introduced, which is now written out by default when casino reads in
formatted bwfn.data files. The previous binary format—bwfn.data.b1—is still supported, not
least because at the time of the introduction of the new format, DFT codes such as pwscf still
produced the old-format b1 file natively (without the intermediate formatted file ever having
existed). By default, b1 files are treated exactly as bin files. If the value of conv binary blips
is set to T, then after reading in a b1 file, the data will be converted and written out as
bwfn.data.bin and the old b1 file will be deleted, prior to continuing the calculation as normal.
This can save disk space since bin files are generally smaller than b1 files and they can be
read in somewhat faster (which is advantageous if the same bin file is to be used in multiple
calculations). The bin files are also more portable. Default value is F.
CUSP CORRECTION (Logical) When expanded in a basis set of Gaussian functions, the
electron–nucleus cusp that should be present in all-electron calculations is not represented correctly.
However, when the cusp correction flag is activated, the s-type Gaussian basis functions
centred on each atom are replaced within a small sphere by a function which ensures that the
electron–nucleus cusp condition is obeyed. This procedure greatly reduces fluctuations in the
local energy in all-electron Gaussian calculations. See Sec. 16 for more details.
CUSP INFO (Logical) If cusp correction is set to T for an all-electron Gaussian basis set calculation,
then casino will alter the orbitals inside a small radius around each nucleus in such a way
that they obey the electron–nucleus cusp condition. If cusp info is set to T then information
about precisely how this is done will be printed to the out file. Be aware that in large systems
this may produce a lot of output. Furthermore, if you create a file called orbitals.in containing
an integer triplet specifying which orbital/ion/spin you want, the code will print graphs
of the specified orbital, radial gradient, Laplacian and ‘one-electron local energy’ to the files
orbitals.dat, gradients.dat, laplacians.dat and local energy.dat. These graphs may
be viewed using xmgrace or similar plotting programs. See Sec. 16 for more details.
CUSP THRESHOLD (Real) If the magnitude of the s component of a Gaussian orbital is less
than this threshold then it will not be cusp corrected. See Sec. 16.
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