2.4. Installation of Dice–Molcas interface for HCI calculations

The Dice–Molcas interface allows one to use heat-bath configuration interaction (HCI) implemented in Dice as an FCI solver in CASSCF calculations, referred to as HCI-CASSCF [16, 17]. A large active space, up to around 100 active orbitals, can be calculated with HCI-CASSCF. Currently, the interface supports ground state HCI-CASSCF calculations.

The interface requires the Dice 1.0 binary (https://github.com/sanshar/Dice). For installation of Dice, consult https://sanshar.github.io/Dice/installation.html. The interface supports both parallel Dice and Molcas.

The Dice–Molcas interface is built by activating in CMake:

-D DICE=ON

Before runing HCI-CASSCF calculations with the Dice–Molcas interface, make sure to increase stack size; and export the Dice binary and all the required libraries for Dice.

ulimit -s unlimited
export PATH=/path/to/dice/binary:$PATH

To run parallel Dice, export the environment variable MOLCAS_DICE, for example when running on 16 nodes use:

export MOLCAS_DICE=16

Verify the installation:

molcas verify .all -w dice