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