For helium-4, we present ab initio, semiclassical calculations of virial coefficients B n for n = 2, 3, 4, and 5 from 50 K to 1000 K. Using our values of B 4 and B 5 and the more accurate literature values of B 2 and B 3 , we argue that the ab initio virial equation of state is more accurate than recent, high-quality, densimeter measurements spanning the range {223 K < T < 500 K, p < 38 MPa}. T...

We propose a novel storage scheme for three-nucleon (3N) interaction matrix elements relevant the normal-ordered two-body approximation used extensively in ab initio calculations of atomic nuclei. This reduces required memory by approximately two orders magnitude, which allows generation 3N with standard truncation ${E}_{3\mathrm{max}}=28$, well beyond previous limit 18. demonstrate that this i...

We present a theoretical approach for ab initio calculations of the one-loop QED corrections to energy levels heavy diatomic quasimolecules. This is based on partial-wave expansion molecular wave and Green's functions in basis monopole solutions, written spherical coordinates. By using so-generated functions, we employ existing atomic-physics techniques evaluate self-energy vacuum-polarization ...

The results of MNDO, AM1 and PM3 semi-empirical calculations and HF/6-31G*, MP/6-31G*, MP2/6-311+G**, and B3LYP/6-311G** and QCISD/6-31G* ab initio methods for angle strain and conjugation effects in twist-boat, boat, and half-chair geometries of (Z,Z,Z)-cycloocta-1,3,5-triene indicate that all methods, except PM3, predict wrong ordering of the conformations.