1. Keywords

CISOlver

Specify the DMRG solver for Molcas. Use CISolver = CheMPS2 in order to run CheMPS2-Molcas interface.

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DMRG

Specify maximum number of renormalized states (or virtual bond dimension m) in each microiteration in DMRG calculations. m must be integer and should be at least 500.

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3RDM

Use this keyword to get the 3-particle and Fock matrix contracted with the 4-particle reduced density matrices (3-RDM and F.4-RDM) for DMRG-CASPT2. Currently, only pseudocanonical basis is supported. OUTOrbitals = CANOnical is automatically activated.

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CHBLb

Specify a threshold for activating restart in CheMPS2. After each macroiteration, if the max BLB value is smaller than CHBLb, activate partial restart in CheMPS2. If the max BLB value is smaller than CHBLb/10.0, activate full restart in CheMPS2. Default value is: 0.5d-2.

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DAVTolerance

Specify value for Davidson tolerance in CheMPS2. Default value is 1.0d-7.

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NOISe

Specify value for noise pre-factor in CheMPS2. This noise is set to 0.0 in the last instruction. Default value (recommended) is: 0.05.

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MXSWeep

Maximum number of sweeps. in the last instruction in CheMPS2. Default value is: 8. In the last iteration of DMRG-SCF, MXSW is increased by five times (default 40).

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MXCAnonical

Maximum number of sweeps in the last instruction with pseudocanonical orbitals in CheMPS2. Default value is: 40.

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CHREstart

Use this keyword to activate restart in the first DMRG iteration from a previous calculation. The working directory must contain molcas_natorb_fiedler.txt and CheMPS2_natorb_MPSx.h5 (x=0 for the ground state, 1 for the first excited state, etc). If these files are not in the working directory, a warning is printed at the beginning of the calculation and restart is skipped (start from scratch).

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DMREstart

Use this keyword to activate restart in the last DMRG iteration from the previous iteration or calculation. This keyword only works when using OUTOrbitals = CANOnical or 3RDM. DMREstart = 0 (default): start from scratch to calculate 3-RDM and F.4-RDM.

DMREstart = 1: start form user-supplied checkpoint files. The working directory must contain molcas_canorb_fiedler.txt and CheMPS2_canorb_MPSx.h5 (x=0 for the ground state, 1 for the first excited state, etc). If these files are not in the working directory, a warning is printed at the beginning of the calculation and restart is skipped (start from scratch).

DMREstart = 2 (Not recommended): start form previous checkpoint files with natural orbitals. DMREstart = 2 is not recommended since this may produce non-optimal energy because the orbital ordering is not optimized.