chemps2 man page

chemps2 — spin-adapted DMRG for ab initio quantum chemistry

Synopsis

chemps2 [OPTION] ...

Description

chemps2 is a scientific code to perform spin-adapted density matrix renormalization group (DMRG) calculations for ab initio quantum chemistry fcidump files. This method allows one to obtain numerical accuracy in active spaces beyond the capabilities of full configuration interaction (FCI) and can return the active space 2-, 3-, and 4-RDM. The method is therefore ideal to replace the FCI solver in the complete active space self consistent field (CASSCF) and complete active space second order perturbation theory (CASPT2) methods. The link to the user manual can be found in the section See Also.

Options

Symmetry

Conventions for the symmetry group and irrep numbers (same as psi4):

                 |  0    1    2    3    4    5    6    7   
        ---------|-----------------------------------------
        0 : c1   |  A                                      
        1 : ci   |  Ag   Au                                
        2 : c2   |  A    B                                 
        3 : cs   |  Ap   App                               
        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 

Arguments

-f, --file=inputfile

Specify the input file.

-v, --version

Print the version of chemps2.

-h, --help

Display this help.

Input File

FCIDUMP = /path/to/fcidump

Note that orbital irreps in the FCIDUMP file follow molpro convention!

GROUP = int

Set the psi4 symmetry group number [0-7] which corresponds to the FCIDUMP file.

MULTIPLICITY = int

Overwrite the spin multiplicity [2S+1] of the FCIDUMP file.

NELECTRONS = int

Overwrite the number of electrons of the FCIDUMP file.

IRREP = int

Overwrite the target wavefunction irrep [0-7] of the FCIDUMP file (psi4 convention).

EXCITATION = int

Set which excitation should be calculated. If zero, the ground state is calculated (default 0).

SWEEP_STATES = int,int,int

Set the number of reduced renormalized basis states for the successive sweep instructions (positive integers).

SWEEP_ENERGY_CONV = flt,flt,flt

Set the energy convergence to stop the successive sweep instructions (positive floats).

SWEEP_MAX_SWEEPS = int,int,int

Set the maximum number of sweeps for the successive sweep instructions (positive integers).

SWEEP_NOISE_PREFAC = flt,flt,flt

Set the noise prefactors for the successive sweep instructions (floats).

SWEEP_DVDSON_RTOL = flt,flt,flt

Set the residual norm tolerance for the Davidson algorithm for the successive sweep instructions (positive floats).

NOCC = int,int,int,int

Set the number of occupied (external core) orbitals per irrep (psi4 irrep ordering).

NACT = int,int,int,int

Set the number of active orbitals per irrep (psi4 irrep ordering).

NVIR = int,int,int,int

Set the number of virtual (secondary) orbitals per irrep (psi4 irrep ordering).

MOLCAS_2RDM = /path/to/2rdm/output

When all orbitals are active orbitals, write out the 2-RDM in HDF5 format when specified (default unspecified).

MOLCAS_3RDM = /path/to/3rdm/output

When all orbitals are active orbitals, write out the 3-RDM in HDF5 format when specified (default unspecified).

MOLCAS_F4RDM = /path/to/f4rdm/output

When all orbitals are active orbitals, write out the 4-RDM contracted with the Fock operator in HDF5 format when specified (default unspecified).

MOLCAS_FOCK = /path/to/fock/input

When all orbitals are active orbitals, read in this file containing the Fock operator (default unspecified).

MOLCAS_FIEDLER = bool

When all orbitals are active orbitals, switch on orbital reordering based on the Fiedler vector of the exchange matrix (TRUE or FALSE; default FALSE).

MOLCAS_ORDER = int,int,int,int

When all orbitals are active orbitals, provide a custom orbital reordering (default unspecified). When specified, this option takes precedence over MOLCAS_FIEDLER.

MOLCAS_MPS = bool

When all orbitals are active orbitals, switch on the creation of MPS checkpoints (TRUE or FALSE; default FALSE).

SCF_STATE_AVG = bool

Switch on state-averaging (TRUE or FALSE; default FALSE).

SCF_DIIS_THR = flt

Switch on DIIS when the update norm is smaller than the given threshold (default 0.0).

SCF_GRAD_THR = flt

Gradient norm threshold for convergence of the DMRG-SCF orbital rotations (default 1e-6).

SCF_MAX_ITER = int

Specify the maximum number of DMRG-SCF iterations (default 100).

SCF_ACTIVE_SPACE = char

Rotate the active space orbitals: no additional rotations (I), natural orbitals (N), localized and ordered orbitals (L), or ordered orbitals only (F) (default I).

SCF_MOLDEN = /path/to/molden

Rotate the FCIDUMP orbitals to the DMRG-SCF occupied (external core), active, and virtual (secondary) orbitals.

CASPT2_CALC = bool

Switch on the CASPT2 calculation (TRUE or FALSE; default FALSE).

CASPT2_ORBS = char

Perform the DMRG calculation for the 4-RDM in the SCF_ACTIVE_SPACE orbitals (A) or in the pseudocanonical orbitals (P) (default A).

CASPT2_IPEA = flt

Ionization potential - electron affinity shift (default 0.0).

CASPT2_IMAG = flt

Imaginary level shift (default 0.0).

CASPT2_CHECKPT = bool

Create checkpoints to continue the CASPT2 4-RDM calculation over multiple runs (TRUE or FALSE; default FALSE).

CASPT2_CUMUL = bool

Use a cumulant approximation for the CASPT2 4-RDM and overwrite CASPT2_CHECKPT to FALSE (TRUE or FALSE; default FALSE).

PRINT_CORR = bool

Print correlation functions (TRUE or FALSE; default FALSE).

TMP_FOLDER = /path/to/tmp/folder

Overwrite the tmp folder for the renormalized operators. With MPI, separate folders per process can (but do not have to) be used (default /tmp).

Example

 $ cd /tmp
 $ wget 'https://github.com/SebWouters/CheMPS2/raw/master/tests/matrixelements/N2.CCPVDZ.FCIDUMP'
 $ ls -al N2.CCPVDZ.FCIDUMP
 $ wget 'https://github.com/SebWouters/CheMPS2/raw/master/tests/test14.input'
 $ sed -i "s/path\/to/tmp/" test14.input
 $ cat test14.input
 $ chemps2 --file=test14.input

Author

Written by Sebastian Wouters <sebastianwouters@gmail.com>

Bugs

Reporting bugs: https://github.com/sebwouters/CheMPS2/issues

See Also

User manual: http://sebwouters.github.io/CheMPS2/index.html

Info

14 November 2016 version 1.8.3 chemps2 v1.8.3