Specialized computational chemistry packages have permanently reshaped the landscape of chemical and materials science by providing tools to support and guide experimental efforts and for the prediction of atomistic and electronic properties. In this regard, electronic structure packages have played a special role by using first-principle-driven methodologies to model complex chemical and materials processes. Over the past few decades, the rapid development of computing technologies and the tremendous increase in computational power have offered a unique chance to study complex transformations using sophisticated and predictive many-body techniques that describe correlated behavior of electrons in molecular and condensed phase systems at different levels of theory. In enabling these simulations, novel parallel algorithms have been able to take advantage of computational resources to address the polynomial scaling of electronic structure methods. In this paper, we briefly review the NWChem computational chemistry suite, including its history, design principles, parallel tools, current capabilities, outreach, and outlook.

The adsorption energies and structures of methanethiolate, SCH3, on the (111) surfaces of Au, Ag, and Cu have been studied using a density functional theory. The results obtained for the Au surface are in good agreement with experiments and previous calculations. The strength of the adsorption energies is found to be Cu>Ag>Au, and the nature of the chemisorption bond is discussed. The strong interaction between the SCH3 and Cu surface can be explained in a similar way to that as for the binding energy of SCH3 with metal atoms. Scalar-relativistic effects in the adsorption energies and adsorption structures, which dominate the differences observed between the Ag and Au surfaces, are studied using quasirelativistic and nonrelativistic pseudopotentials. The relativistic effects decrease the adsorption energy of SCH3 on the Au(111) surface, although the binding energy of the AuSCH3 complex is increased by relativity. The unexpected relativistic effects are also discussed.

of the Small Component 390 2.3.6. Infinite-Order Two-Component Method 391 2.4. ElectronÀElectron Interaction in the DK Hamiltonian 391 2.5. SpinÀOrbit Effects 392 3. Practical Aspects 393 3.1. Implementation of the DK Hamiltonian 393 3.2. Energy Derivatives 394 3.3. Basis Sets 395 3.4. Model Potentials 395 3.5. Program Packages 396 4. Magnetic Properties with the DK Method 396 4.1. NMR Magnetic Shielding Constants 396 4.2. NMR SpinÀSpin Couplings 397 4.3. Magnetizabilities 397 4.4. Zero-Field Splittings 398 4.5. EPR g-Tensors 398 4.6. Hyperfine Coupling Tensors 398 4.7. Magnetic Circular Dichroisms 399 5. Conclusions and Perspectives 399 Biographies 399 Acknowledgment 400 References 400

The higher-order Douglas–Kroll (DK) Hamiltonians in an external potential are explicitly derived. Application of an exponential-type unitary operator with the 2n+1 rule significantly simplifies the formulations of the high-order DK Hamiltonians. The third-order DK method has been implemented practically. Numerical results for one- and many-electron systems show that good accuracy can be obtained even with the DK Hamiltonian correct to third order in the external potential.

We performed a systematic high-throughput simulation with density functional theory for 11 025 compositions of hybrid organic-inorganic halide compounds in ABX and ABB'X forms, where A is an organic or inorganic component, B/B' is a metal atom, and X is a halogen atom. The computational results were compiled as a materials database. We performed massive computational simulation by using the K computer, which is a massively parallel many-core supercomputer in Japan. By applying the screening procedure to all the compounds in the materials database, we discovered novel candidates for environmentally friendly lead-free perovskite solar cells and propose 51 low-toxic halide single and double perovskites, most of which are newly proposed in this study. The proposed low-toxic halide double perovskites are classified under six families: group-14-group-14, group-13-group-15, group-11-group-11, group-9-group-13, group-11-group-13, and group-11-group-15 double perovskites.

Relativistic effects determined using the Douglas-Kroll contracted basis sets and correlation consistent basis sets with small-core relativistic pseudopotentials J. Chem. Phys. 122, 174310 (2005); 10.1063/1.1888571Third-order Douglas-Kroll relativistic coupled-cluster theory through connected single, double, triple, and quadruple substitutions: Applications to diatomic and triatomic hydrides Accurate relativistic Gaussian basis sets determined by the third-order Douglas-Kroll approximation with a finitenucleus model Parallel Douglas-Kroll energy and gradients in NWChem: Estimating scalar relativistic effects using Douglas-Kroll contracted basis sets Highly accurate relativistic Gaussian basis sets are developed for the 103 elements from H (Zϭ1) to Lr (Zϭ103). Orbital exponents are optimized by minimizing the atomic self-consistent field ͑SCF͒ energy with the scalar relativistic third-order Douglas-Kroll approximation. The basis sets are designed to have equal quality and to be appropriate for the incorporation of relativistic effects. The basis set performance is tested by calculations on prototypical molecules, hydrides, and dimers of copper, silver, and gold using SCF, Møller-Plesset theory, and the singles and doubles coupled-cluster methods with and without perturbative triples ͓CCSD, CCSD͑T͔͒. Spectroscopic constants and dissociation energies are reported for the ground state of each species. The effects of relativity, electron correlation, and the basis set superposition error ͑BSSE͒ are investigated. At the BSSE corrected CCSD͑T͒ level, the mean absolute error relative to experiment in D e for three dimers ͑hydrides͒ is 0.13 ͑0.09͒ eV; for R e the error is 0.024 ͑0.003͒ Å, and for e it is 2 ͑13͒ cm Ϫ1 . These illustrative calculations confirm that the present basis sets fulfill their design objectives.

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Using time-dependent density functional theory (TD-DFT), configuration interaction single (CIS) method, and approximate coupled cluster singles and doubles (CC2) method, we investigated the absorption spectra of coumarin derivative dyes (C343, NKX-2388, NKX-2311, NKX-2586, and NKX-2677), which have been synthesized for efficient dye-sensitized solar cells. The CC2 calculations are found in good agreement with the experimental results except for the smallest coumarin dye (C343). TD-DFT underestimates the vertical excitation energy of the larger coumarin dyes (NKX-2586 and -2677). Solvents (methanol) are found to induce a red shift of the vertical excitation energies, and their effects on the molecular geometry and the electronic structure are examined in detail. The deprotonated form of coumarin is also investigated, where a blue shift of the vertical excitation energies is observed.