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_REORDER = 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)."
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/i…

See Also

User manual: http://sebwouters.github.io/CheMPS2/ind…

Info

24 August 2016 version 1.8 chemps2 v1.8