Edward F. Valeev

TL;DR: A wide range of new theoretical methods and analyses have been added to the code base, including functional-group and open-shell symmetry adapted perturbation theory, density-fitted coupled cluster with frozen natural orbitals, orbital-optimized perturbations and coupled-cluster methods, and the "X2C" approach to relativistic corrections, among many other improvements.

TL;DR: The Psi4 program is a new approach to modern quantum chemistry, encompassing Hartree–Fock and density‐functional theory to configuration interaction and coupled cluster and offers flexible user input built on the Python scripting language that enables both new and experienced users to make full use of the program's capabilities.

TL;DR: It is shown that the neglect of electronic polarization leads to qualitatively incorrect values and trends for the transfer integrals computed with the energy splitting method, even in simple prototypes such as ethylene or pentacene dimers.

TL;DR: The results strongly indicate that even greater accuracy may be expected in reactions that preserve (either exactly or approximately) the number and types of chemical bonds.

TL;DR: The new, linear-scaling DLPNO-CCSD(T) implementation typically is 7 times faster than the previous implementation and consumes 4 times less disk space for large three-dimensional systems, and the performance gains and memory savings are substantially larger.