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#basis sets

Every note tagged #basis sets, newest first — or browse the full archive.

July 4, 2026 Chemistry

How much does correlation really cost? The correlation gap in water, measured

The Hartree–Fock post drew its correlation-gap figure schematically. This post runs the actual calculations — RHF marched up a basis-set ladder to its limit, MP2 and CCSD(T) below it — and reports what electron correlation costs, in hartrees, for one bent molecule of water.

#quantum chemistry#Hartree-Fock#electron correlation#basis sets#coupled cluster#psi4
March 22, 2025 Chemistry

Mathematical Frameworks and Basis Sets in Excited State Calculations

A comprehensive explanation of the mathematical principles underlying excited state calculations, including TD-DFT, EOM-CCSD, ADC, and CASSCF methodologies, as well as detailed discussions on basis set selection, computational considerations, and practical applications.

#quantum chemistry#excited states#TD-DFT#EOM-CCSD#basis sets#ADC#CASSCF#benchmark studies
pj Peter V. Johnston

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