Maciej Gutowski

Thermodynamic stability of high-K dielectric metal oxides ZrO2 and HfO2 in contact with Si and SiO2

We present theoretical and experimental results regarding the thermodynamic stability of the high-k dielectrics ZrO2 and HfO2 in contact with Si and SiO2. The HfO2/Si interface is found to be stable with respect to formation of silicides whereas the ZrO2/Si interface is not. The metal–oxide/SiO2 interface is marginally unstable with respect to formation of silicates. Cross-sectional transmission electron micrographs expose formation of nodules, identified as silicides, across the polycrystalline silicon/ZrO2/Si interfaces but not for the interfaces with HfO2. For both ZrO2 and HfO2, the x-ray photoemission spectra illustrate formation of silicate-like compounds in the MO2/SiO2 interface.

THE BASIS SET SUPERPOSITION ERROR IN CORRELATED ELECTRONIC STRUCTURE CALCULATIONS

Abstract A thorough investigation of the proper scheme to correct for basis set superposition errors is performed for the He dimer within the CEPA(1) method. The BSSE proves, even for this small system, extremely difficult to avoid, and it is in no way negligible. Through comparison with perturbation-theory estimates of the interaction energy, we conclude that the full counterpoise correction should be applied rather than a scheme omitting the occupied orbitais of the ghost.

Accuracy of the Boys and Bernardi function counterpoise method

The performance of the Boys and Bernardi function counterpoise (FCP) method in eliminating the basis set superposition error (BSSE) is studied for He2, at R=5.6 a.u., within the supermolecular coupled electron pair approximation (CEPA‐1) method. A series of one‐electron Gaussian basis sets is designed that allows a systematic approach to the basis set limit value of the interaction energy. Every basis set contains a part suitable to reproduce the atomic correlation energy and a second part optimized for the dispersion interaction in He2. BSSE‐free correlated first‐order interaction energies [E(1)], calculated using perturbation theory, are reported for each of these sets. Extrapolation to the basis set limit yields a new value of 33.60±0.02 μH for E(1) at R=5.6 a.u. Extending previous work, the supermolecular CEPA‐1 interaction energies for each set are then compared to the total of E(1) and the BSSE‐free Mo/ller–Plesset second‐order dispersion energy reported previously. While for some basis sets the unc...

Proper correction for the basis set superposition error in SCF calculations of intermolecular interactions

The effects of basis set extension to the space of the partner monomer in supermolecular SCF and perturbation calculations have been analysed for the model He2 and HeLi+ systems. In contrast to the suggestions of many authors it is demonstrated that the correction for the basis set superposition error should be calculated with the full basis set of the dimer without removing the occupied orbitals of the partner monomer. In fact, the enlargement of the monomer basis set by the partner occupied orbitals effectively improves the first-order exchange interaction energy. For the first-order electrostatic interaction energy any enlargement of a poor or medium size basis set of the monomer by the partner orbitals worsens its value.

Relative stabilities of fullerene, cumulene, and polyacetylene structures for Cn:n=18-60

The relative stabilities of closed fullerene, cumulene, and polyacetylene carbon structures, as well as the cohesive energies for clusters of size n=18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 50, and 60 have been examined using ab initio self‐consistent‐field and second‐order Mo/ller–Plesset perturbation theory and analytical derivative geometry optimization methods. These geometries and relative stabilities constitute the primary findings of this work. All calculations were carried out using the disco program with atomic basis sets derived from van Duijneveldt’s carbon (6s,3p) primitive orbital basis set, contracted to [3s2p]. For n≥32, the fullerenes are predicted to be the most stable, and their cohesive energies are predicted to increase monotonically as n varies from 24 to 60. The optimized geometries obtained here are very near those obtained earlier by others for the few species where such data exist. Based on earlier work employing larger atomic orbital bases, the relative energies of the fullerene s...

Critical evaluation of some computational approaches to the problem of basis set superposition error

The basis set extension (BSE) effects such as primary and secondary basis set superposition errors (BSSE) are discussed on the formal and numerical ground. The symmetry‐adapted perturbation theory of intermolecular forces offers an independent reference point to determine efficacy of some computational approaches aiming at elimination of BSSE. The formal and numerical results support the credibility of the function counterpoise method which dictates that the dimer energy calculated within a supermolecular approach decomposes into monomer energies reproduced with the dimer centered basis set and the interaction energy term which also takes advantage of the full dimer basis. Another consistent approach was found to be Cullen’s ‘‘strictly monomer molecular orbital’’ SCF method [J. M. Cullen, Int. J. Quantum Chem. Symp. 25, 193 (1991)] in which all BSE effects are a priori eliminated. This approach misses, however, the charge transfer component of the interaction energy. The SCF and MP2 results obtained withi...

Photoinduced Chemical Dynamics of High-Spin Alkali Trimers

Nanometer-sized helium droplets, each containing about 104 helium atoms, were used as an inert substrate on which to form previously unobserved, spin-3/2 (quartet state) alkali trimers. Dispersed fluorescence measurements reveal that, upon electronic excitation, the quartet trimers undergo intersystem crossing to the doublet manifold, followed by dissociation of the doublet trimer into an atom and a covalently bound singlet dimer. As shown by this work, aggregates of spin-polarized alkali metals represent ideal species for the optical study of fundamental chemical dynamics processes including nonadiabatic spin conversion, change of bonding nature, and unimolecular dissociation.

The impact of higher polarization functions of second-order dispersion energy. Partial wave expansion and damping phenomenon for He2☆

Abstract Convergence properties of the Moller—Plesset dispersion energy with respect to saturation of polarization basis set have been investigated, by means of the partial wave expansion through “i” terms, for the He dimer. The expansion proved to be slowly convergent and ineffective if accurate calculations are aimed at. The damping functions for individual terms have been evaluated and shown to be in good agreement with the semi-empirical ones. The basis set extension effect, occurring when occupied and virtual orbitals of monomers are evaluated with the basis set of a whole dimer, has been found to improve upon the slow convergence of the partial wave expansion. Additional improvement is observed on adding bond-centered functions.

Interpretation of the Hartree-Fock interaction energy between closed-shell systems

In the present paper a decomposition of the Hartree-Fock interaction energy of two closed-shell systems is given. The decomposition is obtained by performing the Hartree-Fock iterations for the supersystem in a way different from the traditional one. The procedure is called the Pauli blockade method since the interacting molecules are deformed in the field of their partners under the constraint that they cannot penetrate each others occupied spaces. The zeroth iteration of the above procedure gives the Heitler-London interaction energy and in the consecutive iterations the total energy of the supersystem is minimized letting the charge distribution of molecule A adapt itself to the presence of molecule B and vice versa, until self-consistency is achieved. It is also shown that unphysical charge transfer may occur in some methods if during mutual deformations the intersystem Pauli exclusion principle is not observed. This confirms earlier suggestions that the so called weak symmetry forcing in the perturba...

How to choose a one‐electron basis set to reliably describe a dipole‐bound anion

The problem of choosing appropriate atomic orbital basis sets for ab initio calculations on dipole-bound anions has been examined. Such basis sets are usually constructed as combination of a standard valence-type basis, designed to describe the neutral molecular core, and an extra diffuse set designed to describe the charge distribution of the extra electron. As part of the present work, it has been found that the most commonly used valence-type basis sets (e.g., 6-31CCG or 6-311CG), when so augmented, are subject to unpredictable under- or overestimating electron binding energies for dipole-bound anions. Whereas, when the aug-cc-pVDZ, aug-cc-pVTZ (or other medium-size polarized (MSP) basis sets) are so augmented, more reliable binding energies are obtained especially when the electron binding energy is calculated at the CCSD(T) level of theory. The issue of designing and centering the extra diffuse basis functions for the excess electron has also been studied, and our findings are discussed here. c 2000 John Wiley & Sons, Inc. Int J Quantum Chem 80: 1024-1038, 2000