CASINO manual - Theory of Condensed Matter
CASINO manual - Theory of Condensed Matter
CASINO manual - Theory of Condensed Matter
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initial configurations come from DMC, in which case the previous DMC best estimate <strong>of</strong> the<br />
energy is used instead.<br />
DMCMD EQUIL NSTEP (Integer) Total number <strong>of</strong> DMC steps performed in the DMC equilibration<br />
stage when we are doing a non-initial step in a DMC molecular dynamics calculation<br />
(we already have a quasi-converged wave function for a slightly different nuclear configuration).<br />
The number <strong>of</strong> blocks is assumed to be 1.<br />
DMCMD STATS NSTEP (Integer) Total number <strong>of</strong> DMC steps performed in the DMC stats accumulation<br />
stage when we are doing a non-initial step in a DMC molecular dynamics calculation<br />
(we already have a quasi-converged wave function for a slightly different nuclear configuration).<br />
The number <strong>of</strong> blocks is assumed to be 1.<br />
DMC MD (Logical) If DMC MD is T then in a DMC calculation we assume we are doing<br />
molecular dynamics and that we are restarting from a converged wave function for a<br />
slightly different nuclear configuration. In practice, all this means is that the number <strong>of</strong><br />
steps performed are given by dmcmd equil nstep and dmcmd stats nstep, rather than<br />
dmc equil nstep/dmc stats nstep (the number <strong>of</strong> blocks is assumed to be 1 in the MD<br />
case). The number <strong>of</strong> moves necessary will be greatly reduced from the normal case. See also<br />
dmc reweight conf and dmc spacewarping. The necessary manipulations are automated<br />
by the runqmcmd script.<br />
DMC METHOD (Integer) dmc method selects which version <strong>of</strong> DMC to use: (1) the particleby-particle<br />
algorithm; (2) the configuration-by-configuration algorithm. Method 1 is the default.<br />
The DMC algorithm is discussed at length in Sec. 13.<br />
DMC NCONF PRELIM (Integer) This is the approximate total number <strong>of</strong> configurations<br />
(summed over all processors) to generate in a preliminary DMC calculation (for reducing the<br />
cost <strong>of</strong> equilibration). See Sec. 13.10.<br />
DMC NORM CONSERVE (Logical) Use the norm-conserving DMC algorithm [16]. This eliminates<br />
fluctuations in the total population. Experimental algorithm: use with caution.<br />
DMC NTWIST (Integer) Number <strong>of</strong> random ‘twists’ or <strong>of</strong>fsets to the grid <strong>of</strong> k vectors to be<br />
sampled during DMC statistics accumulation. If dmc ntwist is 0 then the twist angle is not<br />
changed during DMC. After each change <strong>of</strong> twist angle, the set <strong>of</strong> configurations needs to be reequilibrated:<br />
hence a value needs to be specified for dmc reequil nstep. Setting dmc ntwist<br />
greater than 0 requires the use <strong>of</strong> a complex wave function (complex wf : T). Note that the<br />
usual keywords define the run length for a single twist angle, thus the run length is increased<br />
by a factor <strong>of</strong> dmc ntwist. DMC twist averaging can only be carried out within casino for<br />
electron(-hole) fluid phases at present (for real systems containing atoms, see the utilities in the<br />
<strong>CASINO</strong>/utils/twist directory). See Sec. 28.<br />
DMC POPRENORM (Logical) Control the DMC configuration population by randomly deleting<br />
or copying configurations after branching with the reference energy set equal to the best<br />
estimate <strong>of</strong> the ground-state energy. This can be used to maintain a constant population <strong>of</strong><br />
configurations per core, provided the value <strong>of</strong> dmc target weight is an integer multiple <strong>of</strong> the<br />
number <strong>of</strong> cores. Note that non-integer values <strong>of</strong> dmc target weight are not allowed when<br />
using dmc poprenorm. Note also that dmc poprenorm is not in general recommended because<br />
<strong>of</strong> the population control errors it can theoretically introduce, though in general these are<br />
likely to be small.<br />
DMC REEQUIL NBLOCK (Integer) Number <strong>of</strong> blocks into which the total re-equilibration runlength<br />
is divided when doing a twist-averaged DMC run. Currently, a re-equilibration only takes<br />
place when the twist angle is changed. DMC twist averaging can only be carried out within<br />
casino for electron(-hole) fluid phases at present (for real systems containing atoms, see the<br />
twistav xxx utilities in the <strong>CASINO</strong>/utils/twist directory). See Sec. 28.<br />
DMC REEQUIL NSTEP (Integer) Total number <strong>of</strong> steps performed in the re-equilibration stage<br />
when doing a twist-averaged DMC run. A re-equilibration only takes place when the twist<br />
angle is changed. Notice that this number will be rounded up to the nearest multiple <strong>of</strong><br />
dmc reequil nblock times dmc ave period. DMC twist averaging can only be carried out<br />
within casino for electron(-hole) fluid phases at present (for real systems containing atoms, see<br />
the twistav xxx utilities in the <strong>CASINO</strong>/utils/twist directory). See Sec. 28.<br />
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