The heats of formation of haloacetylenes are evaluated using the recent W1 and W2 ab initio computational thermochemistry methods. These calculations involve CCSD and CCSD(T) coupled cluster methods, basis sets of up to spdfgh quality, extrapolations to the one-particle basis set limit, and contributions of inner-shell correlation, scalar relativistic effects, and (where relevant) first-order s...

A new coupled cluster singles and doubles with triples correction, CCSD(T), algorithm is presented. The new algorithm is implemented in object oriented C++, has a low memory footprint, fast execution time, low I/O overhead, and a flexible storage backend with the ability to use either distributed memory or a file system for storage. The algorithm is demonstrated to work well on single workstati...

A noniterative N(6) triples energy correction is presented for the equation-of-motion coupled-cluster method with single and double substitutions for ionized states (EOM-IP-CCSD). The correction, which is size intensive, is derived using a second-order Rayleigh-Schrodinger perturbative treatment and is similar to the approach of Stanton and Gauss [Theor. Chim. Acta 93, 303 (1996)]. In the prese...

The singlet ground ((approximate)X(1)Sigma1+) and excited (1Sigma-,1Delta) states of HCP and HPC have been systematically investigated using ab initio molecular electronic structure theory. For the ground state, geometries of the two linear stationary points have been optimized and physical properties have been predicted utilizing restricted self-consistent field theory, coupled cluster theory ...

A recent study of the interaction of a lithium atom with the thiophene molecule found a large disagreement between high-level coupled cluster (CCSD(T)/AVTZ) and quantum Monte Carlo (fixed-node diffusion Monte Carlo, or FNDMC) calculations. We address this "lithium-thiophene riddle" by analyzing the influence of crucial FNDMC simulation parameters, namely, the one-electron models, basis sets, an...

The analytic linear response formalism for the calculation of the effective contact densities ρ̅ in the context of the normalized elimination of the small component (NESC) method is developed and implemented. The formalism is tested for the calculation of contact densities and contact density differences in a series of mercury cations and mercury-containing molecules. The calculations carried ou...

An analysis of molecular properties is presented for several first-row diatomic molecules as determined at the CCSD~T! level of theory. In particular, a comparison of spectroscopic constants predicted by the ROHF-CCSD~T! methods of Scuseria vs Gauss et al. is given. Accurate determination of the values of equilibrium bond lengths, dissociation energies, harmonic vibrational frequencies, anharmo...

The gas-phase C-H bond dissociation enthalpy (BDE) in 1,3-cyclopentadiene has been determined by time-resolved photoacoustic calorimetry (TR-PAC) as 358 +/- 7 kJ mol(-1). Theoretical results from ab initio complete basis-set approaches, including the composite CBS-Q and CBS-QB3 procedures, and basis-set extrapolated coupled-cluster calculations (CCSD(T)) are reported. The CCSD(T) prediction for...

This paper provides a compressive sensing (CS) method of denoising images using Bayesian framework. Some images, for example like magnetic resonance images (MRI) are usually very weak due to the presence of noise and due to the weak nature of the signal itself. So denoising boosts the true signal strength. Under Bayesian framework, we have used two different priors: sparsity and clusterdness in...