Title: NIST Scientists Achieve Record Precision in Helium Ground State Calculation
Researchers at the National Institute of Standards and Technology (NIST) have computed the ground state energy of neutral helium with unprecedented accuracy, reaching an estimated precision of one part in 10^20. This represents the highest accuracy calculation of this quantity to date.
To achieve this level of precision, the team employed a novel wave function consisting of a single r12 raised to the first power combined with a conventional non-orthogonal configuration interaction (CI) basis. The computation required very large basis sets, with variational expansions of the wave function using 4,648 terms.
The researchers utilized NIST’s Scientific Computer Facility cluster of 16 PCs running Windows NT for parallel processing, which significantly reduced computation time from 8 hours on a single CPU to 30-40 minutes. The calculation also required 192-bit precision arithmetic, which was simulated using special coding.
The team believes this technique can be extended to other multielectron systems, with work already underway to apply it to atomic lithium. However, this will require a 6000-fold increase in CPU requirements, making the use of parallel programming techniques even more critical.
Keywords: precision, computation, parallel processing, wave function, accuracy
