What Does CCSDTQ Stand For?

CCSDTQ stands for CCSDT With Quadruple Excitations

CCSDTQ, or CCSDT With Quadruple Excitations, is an advanced computational chemistry method that extends the Coupled Cluster with Single, Double, and Triple excitations (CCSDT) approach by incorporating quadruple excitations. This technique significantly enhances the accuracy of electronic structure calculations, particularly for systems where strong correlation effects are present. By accounting for quadruple excitations, CCSDTQ provides a more complete description of electron correlation, making it a powerful tool for studying complex molecular systems and reactions.