Bence

Bence Ladoczki (Budapest University of Technology and Economics)
Explicitly Correlated CCSD(T) Computations with Parallel Implementation
10 March 2026 (Tue) 15:00-16:00 Science and Technology Research Building #4 807 Seminar Room
Abstract
In this talk, I am going to discuss the necessary formalism for a CCSD(T) calculation with explicitly correlated with geminals. Additionally, I am going to talk about the parallel implementation aspects of the tensor operations arising in explicitly correlated CCSD(T). A hybrid Open Multi-Processing (OpenMP)/Message Passing Interface (MPI) parallel approach is used to distribute the computational load among processor cores and compute nodes. The intermediates at both the MP2 and the CCSD(T) levels are expressed in a density fitting formalism, using only three-index quantities to decrease the amount of data to be stored and communicated. To further reduce compute time, the frozen natural orbital, the natural auxiliary function, and the natural auxiliary basis schemes are implemented in a hybrid parallel manner. The combination of these three approximations and our recent size-consistent explicitly correlated triples correction with the new hybrid parallelization offers a unique accuracy-over-cost performance among explicitly correlated CC methods. Our comprehensive benchmarks demonstrate excellent parallel scaling of the cost-determining operations up to hundreds of processor cores. The noncovalent interaction energy (NCIE) of the corannulene dimer is calculated with our new highly accurate explicitly correlated CCSD(T) program tackling 60 atoms and 2500 orbitals, which were beyond computational limits without local correlation approximations.