2.3. Installation of CheMPS2–Molcas interface for DMRG calculations

The CheMPS2–Molcas interface requires the following components: The CheMPS2–Molcas interface [13][14], based on the Block–Molcas interface [15], can support DMRG-SS-CASPT2 and DMRG-SA-CASPT2 calculations.

It requires the CheMPS2 binary. For installation of CheMPS2, consult http://sebwouters.github.io/CheMPS2/index.html if it is not already available in your OS.

Note that only the version with the Open Multi-Processing (OpenMP) is supported, thus build CheMPS2 with:


In order to efficiently run the CheMPS2–Molcas interface, it is advisible to compile either serial or parallel Molcas with MPI. An example:

./configure -compiler intel -parallel -64 -mpiroot /path/to/mpi/root \
            -mpirun /path/to/mpi/bin/mpirun -blas MKL -blas_lib -mkl=sequential \
            -hdf5_inc /path/to/hdf5/include \
            -hdf5_lib /path/to/hdf5/lib \
            -chemps2 /path/to/chemps2/binary

The CheMPS2–Molcas interface can also be activated with CMake:

-D CHEMPS2=ON -D CHEMPS2_DIR=/path/to/chemps2/binary

Before testing the CheMPS2–Molcas interface, make sure to increase stack size, export OMP_NUM_THREADS, the CheMPS2 binary, and all the required libraries for CheMPS2.

ulimit -s unlimited
[export OMP_NUM_THREADS=...]
export PATH=/path/to/chemps2/binary:$PATH

Verify the installation:

molcas verify extra:850,851
molcas verify benchmark:970