mp2f12

An explicity correlated second-order Moeller Plesset perturbation theory plugin to Psi4.

Overview

This plugin to Psi4 performs explicity correlated second-order Moeller Plesset perturbation theory (MP2-F12) computations using the most robust ansatz (3C) within the diagonal orbital-invariant (SP) ansatz of Ten-no (FIX) most commonly seen as MP2-F12/3C(FIX). This particular version of the method scales N⁵. The bulk of the time to compute this plugin is dedicated to formation of the two-electron integrals, which are not screened due to limitations with Psi4.

Installation

Only two main depedencies are needed, with the rest being needed by Psi4 as well.

Psi4

Psi4 may be installed with a conda environment or from source.

Anaconda Envrionment

A new version of python may also be used just check the Psi4 website or the Psi4 Manual.

conda install psi4 python=3.10 -c conda-forge/label/libint_dev -c conda-forge
conda install cmake

Source

1. Clone the Psi4 repo

git clone https://github.com/psi4/psi4.git

Then build as instructed in the Psi4 Manual.

Einsums

Einsums is a submodule of this project.

git submodule init
git submodule update

mp2f12

Once the dependencies are loaded, the plugin can be made.

cmake -S. -Bbuild -DLAPACK_LIBRARIES="/path/to/lib/libcblas.so;/path/to/lib/liblapack.so"
cd build
make
mv mp2f12.so ..

Input Options

• F12_TYPE (string):

  Defines which algorithm to use. Allowed values are CONV, DF, DISK_CONV, and DISK_DF. The default value is CONV.

• F12_INTS_RESTART (bool):

  Turns on the ability to read the integrals from a past computation stored in the Data_*.h5 on disk.

• F12_BETA (double):

  Slater exponent for contracted Gaussian-type geminal. Note that the exponents 0.9, 1.0, and 1.0 a₀^-1 are recommended for cc-pVXZ-F12 where X = D, T, and Q, respectively, while those for aug-cc-pVXZ where X = D, T, and Q are 1.1, 1.2, and 1.4 a₀^-1. The default value is a₀^-1.

• CABS_BASIS (string):

  The CABS recommendations are

  • cc-pVXZ-F12 with cc-pVXZ-F12-OPTRI
  • aug-cc-pVXZ with cc-pVXZ-JKFIT

• CABS_SINGLES (bool):

  Turns on the singles correction, which accounts for the incompleteness error in the Hartree-Fock energy due to the introduction of the CABS. Default value is TRUE.

• DF_BASIS_F12 (string):

  Defines which basis set to use for density-fitting in the F12 computation. Also, sets the DF_BASIS_MP2 for the MP2 computation.