Volume 138, Issue 11, 21 March 2013
Index of content:
138(2013); http://dx.doi.org/10.1063/1.4795430View Description Hide Description
We present an efficient algorithm for evaluating a class of two-electron integrals of the form over one-electron Gaussian basis functions. The full Breit interaction in four-component relativistic theories beyond the Gaunt term is such an operator with n = 3. Another example is the direct spin–spin coupling term in the quasi-relativistic Breit–Pauli Hamiltonian (n = 5). These integrals have been conventionally evaluated by expensive derivative techniques. Our algorithm is based on tailored Gaussian quadrature, similar to the Rys quadrature for electron repulsion integrals (ERIs), and can utilize the so-called horizontal recurrence relation to reduce the computational cost. The CPU time for computing all six Cartesian components of the Breit or spin–spin coupling integrals is found to be only 3 to 4 times that of the ERI evaluation.
Communication: Solvation and dielectric response in ionic liquids—Conductivity extension of the continuum model138(2013); http://dx.doi.org/10.1063/1.4796198View Description Hide Description
The solvation response of a polarity probe in a conducting liquid is analyzed based on simple continuum theory. A multi-exponential description of the dynamics is inverted to give an effective dc conductivity and a generalized permittivity spectrum in terms of Debye modes. For Coumarin 153 in ionic liquids the conductivity is found to be reduced systematically from the bulk value, whereas the permittivity from GHz-THz bulk absorption measurements is well reproduced by the solvation experiment. Thus, by using a dye as molecular antenna, the dielectric dispersion of the microscopic environment can be obtained.