Gaussian Basis Set and Planewave Relativistic Spin-Orbit Methods in NWChem.

Relativistic spin-orbit density functional theory (DFT) methods have been implemented in the molecular Gaussian DFT and pseudopotential planewave DFT modules of the NWChem electronic-structure program. The Gaussian basis set implementation is based upon the zeroth-order regular approximation (ZORA) while the planewave implementation uses spin-orbit pseudopotentials that are directly generated from the atomic Dirac-Kohn-Sham wave functions or atomic ZORA-Kohn-Sham wave functions. Compared to solving the full Dirac equation these methods are computationally efficient but robust enough for a realistic description of relativistic effects such as spin-orbit splitting, molecular orbital hybridization, and core effects. Both methods have been applied to a variety of small molecules, including I2, IF, HI, Br2, Bi2, AuH, and Au2, using various exchange-correlation functionals. Our results are in good agreement with experiment and previously reported calculations.

[1]  W. R. Wadt,et al.  Ab initio effective core potentials for molecular calculations , 1984 .

[2]  Christoph van Wüllen,et al.  Molecular density functional calculations in the regular relativistic approximation: Method, application to coinage metal diatomics, hydrides, fluorides and chlorides, and comparison with first-order relativistic calculations , 1998 .

[3]  Nelson,et al.  First-principles calculations of spin-orbit splittings in solids using nonlocal separable pseudopotentials. , 1993, Physical review. B, Condensed matter.

[4]  Hess,et al.  Applicability of the no-pair equation with free-particle projection operators to atomic and molecular structure calculations. , 1985, Physical review. A, General physics.

[5]  H. Tatewaki,et al.  Chemically reliable uncontracted Gaussian-type basis sets for atoms H to Lr , 2000 .

[6]  A. D. Corso,et al.  Spin-orbit coupling with ultrasoft pseudopotentials: Application to Au and Pt , 2005 .

[7]  Marvin Douglas,et al.  Quantum electrodynamical corrections to the fine structure of helium , 1971 .

[8]  S. Goedecker,et al.  Relativistic separable dual-space Gaussian pseudopotentials from H to Rn , 1998, cond-mat/9803286.

[9]  R. Ahlrichs,et al.  Efficient molecular numerical integration schemes , 1995 .

[10]  J. V. Lenthe,et al.  Note on the calculation of analytical Hessians in the zeroth‐order regular approximation (ZORA) , 2006 .

[11]  A. D. Corso.  Density functional perturbation theory for lattice dynamics with fully relativistic ultrasoft pseudopotentials : Application to fcc-Pt and fcc-Au , 2007 .

[12]  Benny G. Johnson,et al.  A standard grid for density functional calculations , 1993 .

[13]  Tatsuki Oda,et al.  Fully relativistic two-component-spinor approach in the ultrasoft-pseudopotential plane-wave method , 2005 .

[14]  D. Cremer,et al.  A gauge-independent zeroth-order regular approximation to the exact relativistic Hamiltonian--formulation and applications. , 2005, The Journal of chemical physics.

[15]  Ph. Durand,et al.  Regular Two-Component Pauli-Like Effective Hamiltonians in Dirac Theory , 1986 .

[16]  Evert Jan Baerends,et al.  The zero order regular approximation for relativistic effects: the effect of spin-orbit coupling in closed shell molecules. , 1996 .

[17]  Martins,et al.  Efficient pseudopotentials for plane-wave calculations. , 1991, Physical review. B, Condensed matter.

[18]  M. Barysz.  The relativistic scheme for eliminating small components Hamiltonian: Analysis of approximations , 2000 .

[19]  W. R. Wadt,et al.  Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals , 1985 .

[20]  C. W. Murray,et al.  Quadrature schemes for integrals of density functional theory , 1993 .

[21]  Peter J. Knowles,et al.  Improved radial grids for quadrature in molecular density‐functional calculations , 1996 .

[22]  Markus Reiher,et al.  The generalized Douglas–Kroll transformation , 2002 .

[23]  J. G. Snijders,et al.  An ab initio two-component relativistic method including spin- orbit coupling using the regular approximation , 2000 .

[24]  Leonard Kleinman,et al.  Efficacious Form for Model Pseudopotentials , 1982 .

[25]  Evert Jan Baerends,et al.  Relativistic total energy using regular approximations , 1994 .

[26]  N. A. Hill,et al.  First-principles approach to spin-orbit coupling in dilute magnetic semiconductors , 2002 .

[27]  M. L. Tiago,et al.  Real-space pseudopotential method for spin-orbit coupling within density functional theory , 2007 .

[28]  Evert Jan Baerends,et al.  Relativistic regular two‐component Hamiltonians , 1993 .

[29]  K. Dyall.  An exact separation of the spin‐free and spin‐dependent terms of the Dirac–Coulomb–Breit Hamiltonian , 1994 .

[30]  Michael J. Frisch,et al.  Achieving linear scaling in exchange-correlation density functional quadratures , 1996 .

[31]  J. G. Snijders,et al.  Gradients in the ab initio scalar zeroth-order regular approximation (ZORA) approach , 2000 .

[32]  Hamann.  Generalized norm-conserving pseudopotentials. , 1989, Physical review. B, Condensed matter.

[33]  A. Becke.  Correlation energy of an inhomogeneous electron gas: A coordinate‐space model , 1988 .

[34]  Evert Jan Baerends,et al.  Geometry optimizations in the zero order regular approximation for relativistic effects. , 1999 .

[35]  Nicola A. Hill,et al.  Self-consistent treatment of spin-orbit coupling in solids using relativistic fully separable ab initio pseudopotentials , 2001 .