CASINO manual - Theory of Condensed Matter

‘slater-type’: use Slater-type orbitals; the orbitals are read in from stowfn.data;
‘numerical’: use orbitals tabulated on a grid (atomic systems only); the orbitals are read in from
awfn.data;
‘dimer’: use orbitals tabulated on a grid (molecular dimers only); the orbitals are read in from
dwfn.data;
‘blip’: use a blip basis set; the orbitals are read in from bwfn.data.
Some special wave function types are also available:
‘nonint he’: use exact orbitals for a noninteracting helium atom.
‘h2’ or ‘h3plus‘: wave functions for the H 2 molecule or the H + 3 molecular ion where each orbital
is the sum over hydrogen nuclei of a parameter-less exponential centred at each nucleus.
For free-particle and external-potential-related orbitals, set atom basis type to ‘none’ and use
the input block free particles.
BACKFLOW (Logical) Turns on backflow corrections (see Sec. 23). Backflow parameters are read
from correlation.data and, if optimized (opt backflow = T), written to correlation.out.
BF SPARSE (Logical) Setting bf sparse to T will result in the Woodbury formula being used to
update the inverse Slater matrices and determinants instead of recomputing the determinants
entirely. This is advantageous only if the backflow functions are short-ranged with respect to
the size of the system.
BLIP MPC (Logical) If blip mpc is set to T and one is using the MPC interaction in a system that
is periodic in all three dimensions and consists of only electrons then the long-range portion of
the MPC potential will be evaluated using blip functions. In some systems setting this to T can
greatly speed up the calculation. The default is F.
BLIP PERIODICITY (Integer) Orbitals expanded in a blip basis can be periodic in zero, one, two
or three dimensions. blip periodicity specifies the number of dimensions in which the orbitals
are periodic. Note that if blip periodicity is 1 then the system is assumed to be periodic in
the x direction, while if blip periodicity is 2 then the system is periodic in the (x, y) plane.
In all cases, the simulation cell is the parallelepiped defined by the lattice vectors placed at
the origin. ‘Lattice vectors’ in nonperiodic directions should be orthogonal to lattice vectors in
periodic directions. Note that k points may only be used in periodic directions. See Sec. 9.
BSMOOTH (Logical) If bsmooth is set to T then localized orbitals are interpolated smoothly to
zero beyond their cutoff radius. Otherwise, they are truncated abruptly. See Sec. 27 for more
information. It is recommended that bsmooth be set to F, which is the default.
CEREFDMC (Real) Constant used in updating the reference energy in the DMC algorithm. See
Sec. 13.4.
CHECKPOINT (Integer) This integer-valued keyword determines how much casino should worry
about saving checkpoint data to config.out files (which can take a not insignificant amount of
time, especially with large systems done on many cores, and can reduce the parallel efficiency—
since the slower blocking redistribution algorithm must be used at the end of every block when
we write out a config file).). checkpoint can take four values:
‘2’: save data after every block in both VMC and DMC, and save the state of the random
number generator in OPT runs.
‘1’ [default]: as ‘2’, but save data in VMC only after the last block when runtype = vmc opt,
opt vmc or vmc dmc (still after every block if runtype=vmc).
‘0’: only save data at the end of the run, for continuation purposes. This is safe only if used in
conjunction with the max cpu time or max real time keywords (since then the config.out
file will be automatically written if casino sees the job is about to run into an imposed time
limit, even if we have not completed the full number of requested blocks).
‘-1’: do not write config.out file at all, ever (DMC only). Note this value should be chosen
only if you know that the job will fit in any imposed time limit and that such a run will be
long enough to give an acceptably small error bar, since it will be impossible to subsequently
continue the run.
Note checkpoint= 0 or −1 clashes with the DMC catastrophe-recovery facility, for which each
DMC block needs to be checkpointed. The value of checkpoint is thus set to 1 regardless of
the input value if dmc trip weight > 0.
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