Larry McMurchie

One- and two-electron integrals over cartesian gaussian functions

A formalism is developed which allows overlap, kinetic energy, potential energy and electron repulsion integrals over cartesian Gaussian functions to be expressed in a very compact form involving easily computed auxiliary functions. Similar formulas involving the same auxiliary functions are given for the common charge moments, electric-field operators, and spin-interaction operators. Recursion relations are given for the auxiliary functions which make possible the use of Gaussian functions of arbitrarily large angular momentum. An algorithm is described for the computation of electron repulsion integrals.

Placement and routing tools for the Triptych FPGA

Field-programmable gate arrays (FPGAs) are becoming an increasingly important implementation medium for digital logic. One of the most important keys to using FPGAs effectively is a complete, automated software system for mapping onto the FPGA architecture. Unfortunately, many of the tools necessary require different techniques than traditional circuit implementation options, and these techniques are often developed specifically for only a single FPGA architecture. In this paper we describe automatic mapping tools for Triptych, an FPGA architecture with improved logic density and performance over commercial FPGAs. These tools include a simulated-annealing placement algorithm that handles the routability issues of fine-grained FPGAs, and an architecture-adaptive routing algorithm that can easily be retargeted to other FPGAs. We also describe extensions to these algorithms for mapping asynchronous circuits to Montage, the first FPGA architecture to completely support asynchronous and synchronous interface applications.

Configuration interaction calculations on the planar 1(π,π*) state of ethylene

The 1(π,π*) state of ethylene has been thoroughly investigated at the configuration interaction level utilizing an extensive basis set and a configuration selection scheme which emphasizes a correct description of all correlation effects involving the π or π* electrons. The result, contrary to the Hartree–Fock prediction, but in agreement with the general experimental conclusion, is a mostly valence state as indicated by a value for 〈π*‖x2‖π*〉 of 8.8 a.u. using the π* natural orbital. A calculated excitation energy of 7.96 eV is in reasonable agreement with the 7.65 eV experimental absorption maximum. It is found that σ→σ* excitations relative to the ground state are essential to describe the left–right correlation of σ electrons with the π* electron. This in turn compensates for the ionic πA 2–πB 2 nature of the 1(π,π*) state, allowing the SCF state to become contracted at the CI level. The π* orbital in the second 1(π,π*) state appears to be well characterized at a CI level as a 3d orbital constrained t...

Calculation of integrals over ab initio pseudopotentials

An approach is presented for the evaluation of the two distinct types of one-electron integrals arising from the ab initio pseudopotentials introduced by Kahn and Goddard. The integrals are shown to reduce to a sum over products of angular and radial integrals, the latter being approximated by power and asymptotic series combined with appropriate recursion relations. The method is valid for arbitrary angular momenta of both the pseudopotential and the Cartesian Gaussian basis functions.

Singlet Rydberg states of ethylene

A configuration interaction scheme is employed to calculate all n=3 Rydberg states of ethylene derived from the excitation of a π electron. This scheme is designed to account for the small amount of correlation energy of the Ryberg electron and to facilitate calculation of term values from a corresponding calculation on the positive ion. With one exception the results are in agreement with the recent spectral assignments of Mulliken. Both the present results and those of other theoreticians illustrate the difficulties of calculating Rydberg states.

The BK method: Application to methylene

The BK method is compared with conventional CI and other perturbation methods for the 3B1 and 1A1 states of methylene. Use of Rayleigh–Schrodinger perturbation theory for construction of an effective Hamiltonian is seen to be more accurate for estimating the full CI energy limit.

ESR investigation of matrix isolated B 16O and B 17O radicals: Comparison of nuclear hyperfine structure with ab initio calculations

An extensive ESR investigation of the 2Σ B16O and B17O radicals in rare gas matrices has been conducted. Several different trapping sites in neon matrices have been found and investigated as a function of temperature over the range 3–10 K both during and after deposition. Motional averaging of the nuclear hyperfine tensor seems to be occurring for two neon sites and the argon matrix. The large isotropic boron hyperfine coupling of these sites and the 17O hfs show excellent agreement with ab initio theoretical results. BO radicals trapped in a third neon site do not appear to be undergoing motional behavior. Isotropic and dipolar hyperfine parameters for this site show reasonable agreement with theoretical results. BO radicals in one neon site which is extremely sensitive to temperature effects exhibit nearly perfect ’’single‐crystal‐like’’ preferential orientation which has not been previously observed in rare gas matrix ESR studies. The results of this BO investigation help to correct erroneous conclusio...

Output prediction logic: a high-performance CMOS design technique

We present Output Prediction Logic (OPL), a technique that can be applied to conventional CMOS logic families to obtain considerable speedups. When applied to static CMOS, OPL retains the restoring character of the logic family, including its high noise margins. Speedups of 2X to 3X over (optimized) conventional static CMOS are demonstrated for a variety of circuits, ranging from chains of gates, to datapath circuits, ranging from chains of gates, to datapath circuits, and to random logic benchmarks. Such speedups are obtained using identical netlists without remapping. When applied to pseudo-nMOS and dynamic families, in combination with remapping to wide-input NORs, OPL yields speedups of 4X to 5X over static CMOS. Since OPL applied to static CMOS is faster than conventional domino logic, and since it has higher noise margins than domino logic, we believe it will scale much better than domino with future processing technologies.

A theoretical determination of the electron affinity of methylene

Large basis set configuration interaction calculations yield an electron affinity of 0.42 eV for CH2(3B1). Application of an empirical correction, based on the known deficiencies of the basis set and CI method in atomic calculations, suggests that this estimate should be increased to approximately 0.63 eV. This provides futher evidence in favor of a reinterpretation of the photoelectron spectrum work of Zittel et al., which indicated an electron affinity of only 0.210 eV while giving a 3B1–1A1 energy gap of 19.6 kcal/mol.

Distributed-memory parallel routing for field-programmable gate arrays

The problems of placement and routing are without doubt the most time-consuming part of the process of automatically synthesizing and configuring circuits for field-programmable gate arrays (FPGAs). FPGAs offer the ability to quickly reconfigure circuits to support rapid prototyping, emulation, or configurable computing, but the time to perform placement and routing, which can take many hours, has become a serious bottleneck. This problem is addressed here by showing that the negotiation-based routing paradigm, which has been applied successfully in several FPGA routers, can be parallelized to achieve increased performance without any significant decrease in the quality of the results. In this paper, we report several new findings related to the negotiation-based routing paradigm. We examine in-depth the convergence of the negotiation-based routing algorithm. We illustrate that the negotiation-based algorithm can be parallelized. Finally, we demonstrate that a negotiation-based parallel FPGA router performs well in terms of delay and speedup with practical FPGA circuits.