Interface to CheMPS2 by S. Wouters¶

Code author: Sebastian Wouters

Section author: Lori A. Burns

Module: Keywords, PSI Variables, Samples

Note

As of late June 2016, DMRG keywords in PSI4 have been realigned with those of the chemps2 executable, plus a “dmrg_” prefix. The only exceptions are the orbital space PSI4 keywords RESTRICTED_DOCC (formerly CheMPS2 used FROZEN_DOCC, contrary to its definition) and ACTIVE which are passed along to CheMPS2 keywords NOCC and NACT. A translation table is available.

Installation¶

Binary

CheMPS2 is available as a conda package for Linux and macOS (and Windows, through the Ubuntu shell).
If using the PSI4 binary, CheMPS2 has already been installed alongside.
If using PSI4 built from source, and anaconda or miniconda has already been installed (instructions at Quick Installation), CheMPS2 can be obtained through conda install chemps2. Then enable it as a feature with ENABLE_CheMPS2, hint its location with CMAKE_PREFIX_PATH, and rebuild PSI4 to detect CheMPS2 and activate dependent code.

To remove a conda installation, conda remove chemps2.

Source

If using PSI4 built from source and you want CheMPS2 built from from source also, enable it as a feature with ENABLE_CheMPS2, and let the build system fetch and build it and activate dependent code.

Methods¶

Density matrix renormalization group capabilities of PSI4 through CheMPS2¶
name	calls method	Energy	Gradient
dmrg-ci	DMRG configuration interaction (CI)	RHF/ROHF	—
dmrg-scf	DMRG complete active space SCF (CASSCF)	RHF/ROHF	—
dmrg-caspt2	DMRG CAS with 2nd-order perturbation theory (CASPT2)	RHF/ROHF	—

DMRG Keywords¶

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

How to configure CheMPS2 for building Psi4¶

Role and Dependencies

Role — In PSI4, CheMPS2 is a library that provides additional quantum chemical capabilities (DMRG).
Downstream Dependencies — PSI4 (\(\Leftarrow\) optional) CheMPS2
Upstream Dependencies — CheMPS2 \(\Leftarrow\) BLAS/LAPACK, HDF5 \(\Leftarrow\) zlib

CMake Variables

ENABLE_CheMPS2 — CMake variable toggling whether Psi4 builds with CheMPS2
CMAKE_PREFIX_PATH — CMake list variable to specify where pre-built dependencies can be found. For CheMPS2, set to an installation directory containing include/chemps2/DMRG.h
CheMPS2_DIR — CMake variable to specify where pre-built CheMPS2 can be found. Set to installation directory containing share/cmake/CheMPS2/CheMPS2Config.cmake
CMAKE_DISABLE_FIND_PACKAGE_CheMPS2 — CMake variable to force internal build of CheMPS2 instead of detecting pre-built
CMAKE_INSIST_FIND_PACKAGE_CheMPS2 — CMake variable to force detecting pre-built CheMPS2 and not falling back on internal build

Examples

Build bundled

>>> cmake -DENABLE_CheMPS2=ON

Build without CheMPS2

>>> cmake

Build bundled with specific HDF5

>>> cmake -DENABLE_CheMPS2=ON -DCMAKE_PREFIX_PATH=/path/to/hdf5

Link against pre-built

>>> cmake -DENABLE_CheMPS2=ON -DCMAKE_PREFIX_PATH=/path/to/chemps2/root

>>> cmake -DENABLE_CheMPS2=ON -DCheMPS2_DIR=/path/to/chemps2/configdir

Link against pre-built with specific HDF5

>>> cmake -DENABLE_CheMPS2=ON -DCMAKE_PREFIX_PATH="/path/to/chemps2/root;/path/to/hdf5/root"

Build bundled despite pre-built being detectable

>>> cmake -DENABLE_CheMPS2=ON -DCMAKE_PREFIX_PATH=/path/to/unwanted/chemps2/root/and/wanted/other/dependencies/root -DCMAKE_DISABLE_FIND_PACKAGE_CheMPS2=ON

How to fix “`plugin needed to handle lto object`” when building CheMPS2¶

For building with GCC, errors involving unresolved symbols or a message “plugin needed to handle lto object” may indicate a failure of the interprocedural optimization. This can be resolved by passing full locations to gcc toolchain utilities to setup or cmake: -DCMAKE_RANLIB=/path/to/gcc-ranlib -DCMAKE_AR=/path/to/gcc-ar . Details at https://github.com/psi4/psi4/issues/414.