# DMRG

Performs a DMRG computation through calls to Wouters’s CheMPS2 library.

## General

### DMRG_CASPT2_CALC

> Do calculate the DMRG-CASPT2 energy after the DMRGSCF calculations are done?

> - Type: boolean
> - Default: false

### DMRG_CASPT2_IMAG

> CASPT2 Imaginary shift

> - Type: double
> - Default: 0.0

### DMRG_CASPT2_IPEA

> CASPT2 IPEA shift

> - Type: double
> - Default: 0.0

### DMRG_CASPT2_ORBS

> Whether to calculate the DMRG-CASPT2 energy after the DMRGSCF calculations are done.

> - Type: string
> - Possible Values: PSEUDOCANONICAL, ACTIVE
> - Default: PSEUDOCANONICAL

### DMRG_DIIS

> Whether or not to use DIIS for DMRG.

> - Type: boolean
> - Default: false

### DMRG_DIIS_WRITE

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

> - Type: boolean
> - Default: true

### DMRG_EXCITATION

> Which root is targeted: 0 means ground state, 1 first excited state, etc.

> - Type: integer
> - Default: 0

### DMRG_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/doxygen/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_LOCAL_INIT

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

> - Type: boolean
> - Default: true

### DMRG_MOLDEN_WRITE

> DMRG-CI or converged DMRG-SCF orbitals in molden format

> - Type: boolean
> - Default: false

### DMRG_MPS_WRITE

> Whether or not to create intermediary MPS checkpoints

> - Type: boolean
> - Default: false

### DMRG_MULTIPLICITY

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

> - Type: integer
> - Default: -1

### DMRG_OPDM_AO_PRINT

> Print out the density matrix in the AO basis

> - Type: boolean
> - Default: false

### DMRG_PRINT_CORR

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

> - Type: boolean
> - Default: false

### DMRG_SCF_ACTIVE_SPACE

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

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

### DMRG_SCF_DIIS_THR

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

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

### DMRG_SCF_GRAD_THR

> The density RMS convergence to stop an instruction during successive DMRG instructions

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

### DMRG_SCF_MAX_ITER

> Maximum number of DMRG iterations

> - Type: integer
> - Default: 100

### DMRG_SCF_STATE_AVG

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

> - Type: boolean
> - Default: true

### DMRG_SWEEP_DVDSON_RTOL

> The residual tolerances for the Davidson diagonalization during DMRG instructions

> - Type: array
> - Default: No Default

### DMRG_SWEEP_ENERGY_CONV

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

> - Type: array
> - Default: No Default

### DMRG_SWEEP_MAX_SWEEPS

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

> - Type: array
> - Default: No Default

### DMRG_SWEEP_NOISE_PREFAC

> The noise prefactors for successive DMRG instructions

> - Type: array
> - Default: No Default

### DMRG_SWEEP_STATES

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

> - Type: array
> - Default: No Default

### DMRG_UNITARY_WRITE

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

> - Type: boolean
> - Default: true