Multireference Methods for Calculating the Dissociation Enthalpy of Tetrahedral P₄ to Two P₂

Abstract

The potential energy surface for the thermal decomposition of P → 2P was computed along the C reaction trajectory. Single-reference methods were not suitable for describing this complex bond-breaking process, so two multiconfigurational methods, namely, multistate complete active space second-order perturbation theory (MS-CASPT2) and multiconfiguration pair-density functional theory (MC-PDFT), were used with the aim of determining the accuracy and efficiency of these methods for this process. Several active spaces and basis sets were explored. It was found that the multiconfiguration pair-density functional theory method was up to 900 times faster than multistate complete active space second-order perturbation theory while providing similar accuracy.

Stabilizing P≡P: P22–, P2⋅–, and P20 as bridging ligands

“…21,22 We note in passing that P2 oligomerization predominantly yields red phosphorous, 71 while the symmetry-forbidden dimerization is associated with a significant kinetic barrier. 19,72,73 (C) End-on/side-on isomerization of P2 as a terminal ligand and dimerization to complex 7 (cf. ESI for further details).…”

Multiconfiguration Pair-Density Functional Theory for Transition Metal Silicide Bond Dissociation Energies, Bond Lengths, and State Orderings

“…One may approximate the missing correlation energy by using perturbation theory, and here we test this approach by using second order perturbation theory with the CASSCF wave function as the zero-order wave function, which yields the CASPT2 method [ 22 , 23 , 24 ]. We also study an inexpensive alternative to account for electron correlation energy, namely multiconfiguration pair-density functional theory (MC-PDFT) [ 25 , 26 ], which is here applied both with a CASSCF reference function (CAS-PDFT) and with an SP reference function (SP-PDFT) It has been previously shown that the MC-PDFT method has comparable accuracy to that of CASPT2 for dissociation energies, while requiring less computational resources, and it does not suffer from intruder state problems that often plague CASPT2 [ 15 , 26 , 27 , 28 , 29 ].…”

The OpenMolcas Web: A Community-Driven Approach to Advancing Computational Chemistry

“…MC-PDFT is typically as accurate as, and sometimes more accurate than, CASPT2 for vertical excitations, − barrier heights, , singlet–triplet gaps, ,− spin-state orderings, and bond energies. ,,,− …”