Install SCI Solvers

To run SCI as the fragment solver in QuEmb, we interface with cornell-shci, an extension module of PySCF.

To do so, we need to install several packages. Choose some path to hold your SCI solving software, /path/to/software/loc/

Pt. 1: We must first install SHCI, from QMC-Cornell, as described in Arrow's wiki: https://github.com/QMC-Cornell/shci/wiki

The Installation and Compilation instructions should be adequate for this. I am reproducing that code here:

cd `/path/to/software/home/`
git clone --recursive https://github.com/QMC-Cornell/shci
cd shci
make -j

IF you are using an Intel compiler, use make -f Makefile.intel -j. Notes for our MIT cluster: best chance for success: do not use Intel to compile this! Instead, load the appropriate module module load openmpi/3.1.6_gnu, choosing your preferred version

This should fully install SHCI.

Pt. 2: You then must install cornell-shci and tell it where SHCI is installed. To do so, first begin the instructions from PySCF. We recommend using the "custom folder for development" information. https://github.com/pyscf/cornell-shci

Clone the code:

git clone https://github.com/pyscf/cornell-shci /path/to/software/loc/

and make sure that the PYSCF_EXT_PATH is set:

echo 'export PYSCF_EXT_PATH=/path/to/software/loc/cornell-shci:$PYSCF_EXT_PATH' >> ~/.bashrc

by adding the path to cornell-shci in your ~/.bashrc.

cd /path/to/software/loc/cornell-shci
cp pyscf/cornell_shci/settings.py.example pyscf/cornell_shci/settings.py 

In the last settings step, provide the path to SHCI, which was installed in Pt. 1. This should build and allow for you to use cornell-shci, interfaced with PySCF, as a QuEmb SCI solver!