.. _keywords_list:
Keywords
********
Block program offers many keywords to control the calculation. In the Block
input file, each keyword (and its value) should take one line. There are two
types of format to input the keywords. One is the key-value pattern::
keyword value1 value2 ...
The other is the `schedule` section::
schedule
0 50 1.0e-6 1e-06
5 50 1.0e-7 0e-06
end
Hamiltonian Types
=================
Default Hamiltonian type is the chemistry Hamiltonian, in which the
2-electron interaction term is a dense matrix. Block also supports model
Hamiltonians:
heisenberg
No associated value.
hubbard
No associated value.
Algorithm Types
===============
If no algorithm is specified, the default is twodot\_to\_onedot algorithm.
onedot
No associated value.
twodot
No associated value.
twodot\_to\_onedot
followed by a single number to indicate the iteration when to switch from the
two-dot to the one-dot algorithm.
Warm-up Types
=============
If ``warmup`` is not specified, the default is ``local\_0site``.
warmup
followed by one of the following strings.
| local\_0site
| local\_2site
| local\_3site
| local\_4site
| wilson
Solver Types
============
If not specified, default is ``davidson`` solver.
davidson
No associated value
lanczos
No associated value
Orbital Reorder Types
=====================
If not specified, ``fielder`` ordering is used by default.
fiedler
No associated value
gaopt
followed by the filename
reorder
followed by the filename which saves the indices of the reordered orbitals.
noreorder
No associated value
Calculation Types
=================
dmrg
No associated value. This is the default calculation type.
calcoverlap
No associated value. If set, Compute only the overlap of two DMRG wave function.
calchamiltonian
No associated value.
fourpdm (Not support in Block-1.5)
No associated value. If set, besides the regular dmrg calculation, the
program also compute the 4-particle density matrix.
fullrestart
No associated value
nevpt2\_npdm
No associated value
onepdm
No associated value, If set, the program also computes and stores the
1-particle density matrix in :file:`spatial_onepdm.*.*.txt`.
restart\_fourpdm
No associated value
restart\_nevpt2\_npdm
No associated value
restart\_onepdm
No associated value
restart\_threepdm
No associated value
restart\_tran\_onepdm
No associated value
restart\_tran\_twopdm
No associated value
restart\_twopdm
No associated value
threepdm
No associated value, If set, the program also computes and stores the
3-particle density matrix in :file:`spatial_threepdm.*.*.txt`.
transition\_onepdm
No associated value, If set, the program also computes and stores the
transition density matrix in :file:`spatial_onepdm.*.*.txt`.
transition\_twopdm
No associated value, If set, the program also computes and stores the
transition 2-particle density matrix in :file:`spatial_twopdm.*.*.txt`.
twopdm
No associated value, If set, the program also computes and stores the
2-particle density matrix in :file:`spatial_twopdm.*.*.txt`.
Schedule
========
DMRG sweep schedule. It supports two types of input format. One is::
schedule default
to generate the sweep schedule by Block program. This is the default value of
``schedule`` keyword. The other is to explicitly input the schedule, eg::
schedule
0 50 1.0e-6 1e-06
5 50 1.0e-7 0e-06
end
The first column is the sweep-iteration, the second column is the corresponding
bond dimension, the third column is the convergence tolerance for Davidson
diagonalization, the fourth column is the noise.
Expert Keywords
===============
backward
No associated value. If set, the program starts with backward sweep.
hf\_occ
The initial HF wave function occupancies, in spin orbital. It can be one of
the following values. The recommended one is ``integral``.
integral
Generate occupancy pattern based on the 1-electron integrals.
canonical
Based on the input orbital ordering, take the first N orbitals as occupied
orbitals
manual
followed by the HF occupancy in the same line.
irrep
followed by one or two numbers. If one number is given, it determines the wave
function symmetry. If two numbers are given, it means that calculations of
transition density matrix between wavefunctions with different irreps. The
irrep value follows the Molpro symmetry convention, see also
https://github.com/pyscf/dmrgscf/blob/master/pyscf/dmrgscf/dmrg_sym.py
lastM
followed by an integer. Default is 500
maxiter
followed by an integer represents the max sweep iterations. Default is 10.
maxM
followed by an integer, the maximum bond dimension.
nelec
followed by an integer, for the total number of electrons.
.. new\_npdm\_code
nonspinadapted
No associated value.
nroots
followed by one integer, for the number of states to solve. Default is 1.
.. occ nocc
.. followed by one integer, for the number of occupied orbitals.
orbitals
followed by the orbital file
outputlevel **0** `|| 1 || 2 || 3`
followed by an integer, range from 0 (less output) to 3 (very noise). Default is 0.
.. pdm\_unsorted
scratch
followed by the scratch directory to store the intermediates, the resultant
wave function, and density matrices.
screen\_tol
followed by a float number. Default is 0.0
spin `2S`
followed by an integer represents the difference of alpha and beta electron
numbers.
startM
followed by an integer. Default is 250.
statespecific
No associated value. This option implies that a previous dmrg calculation has
already been performed. This calculation will take the previous wavefunctions
and refine them.
sweep\_tol
followed by a float number, for the convergence tolerance.
sym
followed by the string for the symbol of point group symmetry, can be d2h and
its subgroup.
weights
followed by a list of float numbers for weight of each state. You could chose
to omit the keyword weights in which case the weights will be distributed
uniformly bet ween the different roots.
num_thrds (new in Block-1.5)
followed by an integer for the number of OpenMP threads to use.
memory (new in Block-1.5)
followed by an integer and a letter as the unit (k, m, g).
The default is ``2 g`` (2 GB memory).