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29.2.2 Restarting calculations

The BLOCK program periodically checkpoints the calculation. To restart a DMRG calculation from a saved checkpoint, use the following command,

restart, FCIDUMP=dumpfile_name, SCRATCH=dir_name
where dumpfile_name and dir_name, are the name of the orbitals file and scratch directory, respectively.


Table 15: Full options for BLOCK
Option Alias Default value$^a$ Meaning
MAXM   500 Maximum size of blocks; must always be specified
FIEDLER   1 Default ordering optimization
GAOPT   0 Orbital ordering optimization
REORDERORB   1 If 0, turn off all orbital ordering
MAXITER   30 Maximum no. of sweep iterations
SWEEP_TOL   1E-09 Sets the final DMRG tolerance
ONEDOT   0 One-dot sweeps only
TWODOT   0 Two-dot sweeps only
ONEPDM   0 Calculates the 1-PDM
TWOPDM   0 Calculates the 2-PDM
DRYRUN   0 Writes FCIDUMP and DMRG input file only
RESTART   0 DMRG restart
FCIDUMP   NA For restart only. Specify name of dump file
SCRATCH   NA For restart only. Specify name of the scratch directory
IRREP   1 Irreducible representation of state
NROOTS   1 Number of roots in state-averaged calculation
OUTPUTLEVEL   0 Set to -1 for more verbose molpro output, 1 for full output
NELEC   -1 Number of electrons
TWODOT_TO_ONEDOT   -1 Switch from two-dot to one-dot
a) -1 means default value taken from BLOCK

Examples:

Closed-shell ground-state calculations for sto-3g(10$e^-$, 7$o$) H$_2$O using default parameters.

h2o_dmrg.com

 METHOD                 E
 HF               -74.961135
 DMRG (M=50)      -75.017832
 FCI (comparison) -75.017832

Closed-shell ground-state calculations for the localized $\pi$-active space (8$e^-$, 8$o$) of octatetraene in minimal basis using default parameters.

octatetraene_dmrg.com

 METHOD                 E
 HF                -304.80229195
 DMRG              -304.97074163
 FCI (comparison)  -304.97074163

An example of a non-default orbital ordering and non-default scheduling for the localized $\pi$-active space (18$e^-$, 18$o$) of tetracene in minimal basis. tetracene_dmrg.com

 METHOD                 E
 HF                -680.245827
 DMRG (M=100)      -680.349299
 DMRG (M=250)      -680.578887


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