Accuracy of Effective Core Potentials and Basis Sets for Density Functional Calculations, Including Relativistic Effects, As Illustrated by Calculations on Arsenic Compounds

2011 ◽  
Vol 7 (9) ◽  
pp. 2766-2779 ◽  
Author(s):  
Xuefei Xu ◽  
Donald G. Truhlar
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Relativistic Effects ◽  
Basis Sets ◽  
Arsenic Compounds ◽  
Effective Core Potentials

Introduction to Relativistic Quantum Chemistry

2007 ◽  
Author(s):  
Kenneth G. Dyall ◽  
Knut Faegri
Keyword(s):  
Dirac Equation ◽  
Quantum Chemistry ◽  
Relativistic Theory ◽  
Density Functional ◽  
Relativistic Quantum ◽  
Relativistic Effects ◽  
Basis Sets ◽  
Spin Orbit ◽  
Approximate Methods ◽  
Nonrelativistic Theory

This book provides an introduction to the essentials of relativistic effects in quantum chemistry, and a reference work that collects all the major developments in this field. It is designed for the graduate student and the computational chemist with a good background in nonrelativistic theory. In addition to explaining the necessary theory in detail, at a level that the non-expert and the student should readily be able to follow, the book discusses the implementation of the theory and practicalities of its use in calculations. After a brief introduction to classical relativity and electromagnetism, the Dirac equation is presented, and its symmetry, atomic solutions, and interpretation are explored. Four-component molecular methods are then developed: self-consistent field theory and the use of basis sets, double-group and time-reversal symmetry, correlation methods, molecular properties, and an overview of relativistic density functional theory. The emphases in this section are on the basics of relativistic theory and how relativistic theory differs from nonrelativistic theory. Approximate methods are treated next, starting with spin separation in the Dirac equation, and proceeding to the Foldy-Wouthuysen, Douglas-Kroll, and related transformations, Breit-Pauli and direct perturbation theory, regular approximations, matrix approximations, and pseudopotential and model potential methods. For each of these approximations, one-electron operators and many-electron methods are developed, spin-free and spin-orbit operators are presented, and the calculation of electric and magnetic properties is discussed. The treatment of spin-orbit effects with correlation rounds off the presentation of approximate methods. The book concludes with a discussion of the qualitative changes in the picture of structure and bonding that arise from the inclusion of relativity.

On the dissociation energy of Ti(OH2)+. An MCSCF, CCSD(T), and DFT study

1996 ◽  
Vol 74 (10) ◽  
pp. 1824-1829 ◽  
Author(s):  
A. Irigoras ◽  
J.M. Ugalde ◽  
X. Lopez ◽  
C. Sarasola
Keyword(s):  
Dissociation Energy ◽  
Density Functional ◽  
Basis Sets ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Self Consistent Field Theory ◽  
Effective Core Potentials

The dissociation energy of the Ti(OH2)+ ion–molecule complex was calculated by the multiconfigurational self-consistent field theory, coupled cluster theory, and two density functional theory based methods, using both all-electron basis sets and effective core potentials. The calculations show that approximate density functional theory gives results in better agreement with experiment than either the multiconfigurational self-consistent field theory or the coupled cluster theory, with both all-electron basis sets and effective core potentials. Nevertheless, the optimized geometries and harmonic vibration frequencies are very similar, irrespective of the level of theory used. The interconfigurational energy ordering of the two valence electronic configurations dn−1s and dn−2s2 of the 4F electronic state of the titanium cation were also calculated and are discussed. Key words: ab initio, dissociation energy, ion–molecule complex, effective core potentials, transition metals.

Density functional calculations of Ge(105): Local basis sets andO(N)methods

2007 ◽  
Vol 76 (11) ◽  
Author(s):  
T. Miyazaki ◽  
D. R. Bowler ◽  
R. Choudhury ◽  
M. J. Gillan
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Basis Sets ◽  
Local Basis ◽  
Local Basis Sets

Wechselwirkungen in Molekülkristallen, 127 [1] Die unterschiedlichen Strukturen des im Kristall verdrillten 1,4-Bis(tricyanvinyl)- benzols sowie des eingeebneten 1-Tricyanvinylbenzols, Dichtefunktional- Berechnungen und cyclovoltammetrisch sowie ESR/ENDOR-spektroskopisch charakterisiertes Reduktionsverhalten / Interactions in Molecular Crystals, 127 [1]The Different Structures in the Crystal of Twisted 1,4-Bis(tricyanovinyl)benzene as well as of Planar 1-Tricyanovinyl-benzene, Density Functional Calculations and Reduction Behaviour Studied by Cyclovoltammetry and ESR/ENDOR Spectroscopy

1997 ◽  
Vol 52 (9) ◽  
pp. 1125-1138 ◽  
Author(s):  
Hans Bock ◽  
Wolfgang Seitz ◽  
Norbert Nagel ◽  
Rüdiger Baur ◽  
Jan W. Bats ◽  
...  
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Basis Sets ◽  
General Interest ◽  
Molecular Anion ◽  
Substituent Group ◽  
Endor Spectroscopy ◽  
Disubstituted Benzene ◽  
Disubstituted Derivative ◽  
Reduction Behaviour

The attempted crystal growth of 1,4-bis(tricyanovinyl)benzene dianion salts, although without success so far, has provided information of general interest. The crystal structures of the related mono and 1,4-bis(tricyanovinyl)benzene derivatives differ considerably in their substituent group twisting angles: The two tricyanovinylbenzenes in split-positions exhibit dihedral angles of only 6° or 11°, whereas the two C2(CN)3 groups of the disubstituted benzene are conrotationally twisted by 48° out of the benzene plane. Density functional calculations with 6 - 311++G** basis sets, however, predict identical values of 32° for both compounds and, therefore, their crystal arrangements are discussed in detail for packingenforced additional interactions. Cyclovoltammetric and ESR/ENDOR-measurements provide information on the redox behaviour, a prerequisite for attempts to crystallize molecular anion salts: The 1,4-disubstituted derivative with a cyclovoltammetrically determined halfwave reduction potential of +.14 V in aprotic THF solution proves to be one of the strongest polycyano-substituted π-acceptors and its radical anion can be selectively generated by T1 metal reduction as confirmed by its ESR/ENDOR spectra.

Response Function Basis Sets:  Application to Density Functional Calculations

1996 ◽  
Vol 100 (15) ◽  
pp. 6231-6235 ◽  
Author(s):  
Gerald Lippert ◽  
Jürg Hutter ◽  
Pietro Ballone ◽  
Michele Parrinello
Keyword(s):  
Response Function ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Basis Sets

What Silicon Nanocluster is Most Likely Formed in Etching Experiments? Theoretical DFT Study

2008 ◽  
Vol 8 (7) ◽  
pp. 3478-3482
Author(s):  
Nurbosyn U. Zhanpeisov ◽  
Hiroshi Fukumura
Keyword(s):  
Absorption Spectra ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Electrochemical Etching ◽  
Time Dependent ◽  
Cluster Models ◽  
Dft Study ◽  
Basis Sets ◽  
Self Healing ◽  
Tddft Calculations

Density functional calculations at the B3LYP/6-31G* level were performed for Si nanoclusters of ca.1 nm in size. The structural, energetic, electronic as well as the estimated absorption spectra by the time-dependent DFT (TDDFT) calculations using varied functionals and basis sets for the representative cluster models are all in favor of the formation of most probable Si35H36 nanocluster in recent electrochemical etching experiments. The nanostructure has a complete H-termination at the borderline regions and lacks from the presence of any defects like surface Si—Si dimer units formed via self-healing of dangling Si—Si bonds or from any relatively short H…H contacts.

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