# DMRG

## General

### ACTIVE

> Active space orbitals for DMRGSCF, per irrep. Same conventions as for other MR methods.

> - Type: array
> - Default: No Default

### DMRG_ACTIVE_SPACE

> Which active space to use for DMRGSCF calculations: –> input with SCF rotations (INPUT); –> natural orbitals (NO); –> localized and ordered orbitals (LOC)

> - Type: string
> - Possible Values: INPUT, NO, LOC
> - Default: INPUT

### DMRG_AVG_STATES

> Whether or not to use state-averaging for roots >=2 with DMRG-SCF.

> - Type: boolean
> - Default: true

### DMRG_CHKPT

> Whether or not to create intermediary MPS checkpoints

> - Type: boolean
> - Default: false

### DMRG_DIIS_BRANCH

> When the update norm is smaller than this value DIIS starts.

> - Type: double
> - Default: 1e-2

### DMRG_DO_DIIS

> Whether or not to use DIIS for DMRGSCF.

> - Type: boolean
> - Default: false

### DMRG_E_CONVERGENCE

> The energy convergence to stop an instruction during successive DMRG instructions

> - Type: array
> - Default: No Default

### DMRG_LOC_RANDOM

> Whether to start the active space localization process from a random unitary or the unit matrix.

> - Type: boolean
> - Default: true

### DMRG_MAXITER

> Maximum number of DMRGSCF iterations

> - Type: integer
> - Default: 100

### DMRG_MAXSWEEPS

> The maximum number of sweeps to stop an instruction during successive DMRG instructions

> - Type: array
> - Default: No Default

### DMRG_NOISEPREFACTORS

> The noiseprefactors for successive DMRG instructions

> - Type: array
> - Default: No Default

### DMRG_PRINT_CORR

> Whether or not to print the correlation functions after the DMRG calculation

> - Type: boolean
> - Default: true

### DMRG_STATES

> The number of reduced renormalized basis states to be retained during successive DMRG instructions

> - Type: array
> - Default: No Default

### DMRG_STORE_DIIS

> Whether or not to store the DIIS checkpoint on disk (convenient for restarting).

> - Type: boolean
> - Default: true

### DMRG_STORE_UNIT

> Whether or not to store the unitary on disk (convenient for restarting).

> - Type: boolean
> - Default: true

### DMRG_WFN_IRREP

> The DMRG wavefunction irrep uses the same conventions as PSI4. How convenient :-). Just to avoid confusion, it’s copied here. It can also be found on http://sebwouters.github.io/CheMPS2/classCheMPS2_1_1Irreps.html . Symmetry Conventions Irrep Number & Name Group Number & Name 0 1 2 3 4 5 6 7 0: c1 A 1: ci Ag Au 2: c2 A B 3: cs A’ A’’ 4: d2 A B1 B2 B3 5: c2v A1 A2 B1 B2 6: c2h Ag Bg Au Bu 7: d2h Ag B1g B2g B3g Au B1u B2u B3u

> - Type: integer
> - Default: -1

### DMRG_WFN_MULTP

> The DMRG wavefunction multiplicity in the form (2S+1)

> - Type: integer
> - Default: -1

### DMRG_WHICH_ROOT

> Which root is targeted: 1 means ground state, 2 first excited state, etc.

> - Type: integer
> - Default: 1

### D_CONVERGENCE

> Convergence threshold for the gradient norm.

> - Type: conv double
> - Default: 1e-6

### FROZEN_DOCC

> Doubly occupied frozen orbitals for DMRGSCF, per irrep. Same conventions as for other MR methods

> - Type: array
> - Default: No Default