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1.
Contracted Gaussian-type function sets are developed for correlating p, d, and f functions for a valence electron of the
hydrogen atom and alkali-metal atoms from Li to Rb. A segmented contraction scheme is used for its compactness and efficiency.
Contraction coefficients and exponents are determined by minimizing the deviation from the K orbitals of the atoms. The present basis sets yield an accuracy comparable to the correlation-consistent basis set for the
hydrogen atom and also give a similar high accuracy for the alkali-metal atoms. In the calculations of spectroscopic constants
of alkali hydrides, the decontraction of the p function plays an important role, especially for LiH. The contributions of
d and f functions are nontrivial for KH and RbH.
Received: 6 September 2002 / Accepted: 13 November 2002 / Published online: 19 March 2003
Acknowledgements. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education of Japan.
Correspondence to: T. Noro e-mail: tashi@sci.hokudai.ac.jp 相似文献
2.
Adding the tight and diffuse Gaussian-type functions (GTFs), Faegri's variationally determined double-zeta-quality basis
sets for molecular relativistic calculations are examined. An example atom is Cm. When the tight s-type GTF is added the total
energy increases, whereas when diffuse GTFs are added the total energy decreases. The reasons for these findings are clarified.
It is also pointed out that not only the Faegri's sets but also other variationally determined basis sets would show similar
behavior so far as the expansion terms are not sufficient.
Received: 22 July 2002 / Accepted: 21 October 2002 / Published online: 31 January 2003
Correspondence to: H. Tatewaki e-mail: htatewaki@nsc.nagoya.cu.ac.jp 相似文献
3.
The valence quality of contracted (C) Gaussian-type function (GTF) basis sets in molecular calculations is discussed for the first- through fourth-row atoms. The split-valence basis sets derived from minimal-type CGTF sets are compared with those derived from primitive (P) GTF sets. Using F, Cl, Br, and I atoms and their homonuclear diatomics as test species, we find that the split-valence CGTF sets have almost the same quality as PGTF sets with larger s and p expansion terms: for example, the (53/5), (533/53), (5333/533/5), and (53 333/5333/53) CGTF sets correspond approximately to the [9/5], [15/9], [19/15/5], and [22/18/7] PGTF sets for the first- to fourth-row atoms, respectively, where the slash separates the s, p, and d symmetries. For the main group atoms of the four rows, we recommend using the above-mentioned CGTFs or larger. 相似文献
4.
5.
6.
A number of configurations of NLi
n
Na2 (n = 1–4) species were optimized using the B3LYP–density functional theory method; the 6-31G* basis set was used in this calculation. In order to study all possible dissociation energies, some related species such as
NLi2Na, NLi
n
(n = 1–4), Li
n
(n = 1, 2) and Na
n
(n = 1, 2) were also considered. Optimizations of these species were followed by fundamental frequency calculations at the same
level. Global minima of these species were shown to adopt C
2
v
(NLi4Na2, NLi2Na2), D
3
h
(NLi3Na2) and C
s
(NLiNa2 and NLi2Na) configurations. All possible dissociation energies were obtained.
Received: 30 November 1998 / Accepted: 15 October 1999 / Published online: 14 March 2000 相似文献
7.
Jordi Poater Miquel Solà Miquel Duran Xavier Fradera 《Theoretical chemistry accounts》2002,107(6):362-371
Localization, λ(A), and delocalization indices, δ(A,B), as defined in the atoms in molecules theory, are a convenient tool for the analysis of molecular electronic structure from
an electron-pair perspective. These indices can be calculated at any level of theory, provided that first- and second-order
electron densities are available. In particular, calculations at the Hartree–Fock (HF) and configuration interaction (CI)
levels have been previously reported for many molecules. However, λ(A) and δ(A,B) cannot be calculated exactly in the framework of Kohn–Sham (KS) density functional theory (DFT), where the electron-pair
density is not defined. As a practical workaround, one can derive a HF-like electron-pair density from the KS orbitals and
calculate approximate localization and delocalization indices at the DFT level. Recently, several calculations using this
approach have been reported. Here we present HF, CI and approximate DFT calculations of λ(A) and δ(A,B) values for a number of molecules. Furthermore, we also perform approximate CI calculations using the HF formalism to obtain
the electron-pair density. In general, the approximate DFT and CI results are closer to the HF results than to the CI ones.
Indeed, the approximate calculations take into account Coulomb electron correlation effects on the first-order electron density
but not on the electron-pair density. In summary, approximate DFT and CI localization and delocalization indices are easy
to calculate and can be useful in the analysis of molecular electronic structure; however, one should take into account that
this approximation increases systematically the delocalization between covalently bonded atoms, with respect to the exact
CI results.
Received: 13 February 2002 / Accepted: 24 April 2002 / Published online: 18 June 2002 相似文献
8.
Hiroshi Tatewaki Toshikatsu Koga Shigeyoshi Yamamoto 《Theoretical chemistry accounts》2000,105(1):55-61
For the valence 4p orbitals of the first-row transition metal atoms Sc through Zn, Gaussian-type basis functions are developed referring to
excited 3d
m
4s
14p
1 electronic configurations. Molecular tests of the present work 4p sets are performed for the Cu atom, the diatomic Cu2 molecule, and Cu9 and Cu13 clusters, and the results are compared with those from two literature sets.
Received: 17 January 2000 / Accepted: 30 May 2000 / Published Online: 11 September 2000 相似文献
9.
We discuss the classical dynamics of a CH-stretching and an OH-stretching vibration coupled to a hindered rotation around
a CC (OC) bond of a CH3 group or an OH group. Our model is based on a two-dimensional system, in which zero angular momentum is assumed. The model
is further simplified by considering only kinetic coupling between the CH (OH) stretching and the hindered rotation. Through
numerical calculations, a new set of states is found, which originates from n:1 resonances between the internal rotation frequency and the stretching frequency, n being associated to the order of symmetry (n = 3 and 6 for the cases investigated). We also present a perturbative approach based on the Lie series method, which provides
insight into these nonadiabatic states.
Received: 28 April 1999 / Accepted: 21 September 1999 / Published online: 15 December 1999 相似文献
10.
Masao Masamura 《Theoretical chemistry accounts》2001,106(4):301-313
For the intermolecular interaction energies of ion-water clusters [OH−(H2O)
n
(n=1,2), F−(H2O), Cl−(H2O), H3O+(H2O)
n
(n=1,2), and NH4
+(H2O)
n
(n=1,2)] calculated with correlation-consistent basis sets at MP2, MP4, QCISD(T), and CCSD(T) levels, the basis set superposition
error is nearly zero in the complete basis set (CBS) limit. That is, the counterpoise-uncorrected intermolecular interaction
energies are nearly equal to the counterpoise-corrected intermolecular interaction energies in the CBS limit. When the basis
set is smaller, the counterpoise-uncorrected intermolecular interaction energies are more reliable than the counterpoise-corrected
intermolecular interaction energies. The counterpoise-uncorrected intermolecular interaction energies evaluated using the
MP2/aug-cc-pVDZ level is reliable.
Received: 14 March 2001 / Accepted: 25 April 2001 / Published online: 9 August 2001 相似文献
11.
12.
Multicenter integrals appearing in the Hartree–Fock–Roothaan equations for molecules are calculated using different kinds
of series expansion formulas obtained from the expansions of integer and noninteger n Slater-type orbitals, in terms of Ψ
α
-exponential-type orbitals (where α=1, 0, –1, –2,...) at a displaced center, that form complete orthonormal sets and are represented by linear combinations of
integer n Slater-type orbitals. The convergence of these series is tested by calculating concrete cases. The accuracy of the results
is quite high for quantum numbers, screening constants, and location of orbitals.
Received: 13 February 2002 / Accepted: 11 March 2002 / Published online: 4 July 2002 相似文献
13.
Friedrich Grein 《Theoretical chemistry accounts》2003,109(5):274-277
Using 6-31G and 6-311G basis sets to which diffuse and polarization functions were added in a stepwise fashion (a total of
16 basis sets), Hartree–Fock (HF), MP2 and B3LYP geometry optimizations were performed on biphenyl. With the MP2 method, diffuse
functions raise the dihedral angle φ, for example, from 46.3° for 6-31G to 54.1° for 6-311++G, while polarization functions
lower it, for example, from 54.1° for 6-311++G to 42.1° for 6-311++G(2d,2p). For a single set of polarization functions, φ(MP2)
lies close to or above φ(HF) (44–47°), but for a double set it is below φ(HF) and is close to B3LYP values (38–42°) which
show little basis set dependence. The most reliable value for φ, 42.1° [MP2/6-311++G(2d,2p)], is expected to increase slightly
by adding more diffuse functions. The corresponding best calculated energy barrier at 0° (coplanar conformation) is 2.83 kcal/mol,
much higher than the experimental estimate (1.4 ± 0.5 kcal/mol). The barrier at 90° is 1.82 kcal/mol, in line with the experimental
estimate (1.6 ± 0.5 kcal/mol) and with previous theoretical results.
Received: 9 September 2002 / Accepted: 15 November 2002 /
Published online: 1 April 2003
Correspondence to: Friedrich Grein e-mail: fritz@unb.ca
Acknowledgement. The author would like to thank NSERC (Canada) for financial support. 相似文献
14.
Pseudopotential ab initio calculations were performed for species of the type BH
n
(AuPH3)
m
k
, where n+m=3 or 4, and the charge k is −2,…,+1. Some derivatives of these and diaurated diboranes were also studied. The structural data agree well with the
available experimental evidence. Factors affecting the stability of these systems, including the role of aurophilic attraction,
are discussed. The singly charged anions and the diaurated diboranes are predicted to be the most stable members of these
series.
Received: 22 January 1999 / Accepted: 2 June 1999 / Published online: 4 October 1999 相似文献
15.
16.
Amy J. Austin Michael J. Frisch John A. Montgomery George A. Petersson 《Theoretical chemistry accounts》2002,107(3):180-186
An overlap criterion is defined that connects the identification of core orbitals in a molecular system, which can be problematic,
to that in isolated atoms, which is well defined. This approach has been tested on a variety of troublesome systems that have
been identified in the literature, including molecules containing third-row main-group elements, and is shown to remove errors
of up to 100 kcal/mol arising from an inconsistent treatment of core orbitals at different locations on a potential-energy
surface. For some systems and choices of core orbitals, errors as large as 19 kcal/mol can be introduced even when consistent
sets of orbitals are frozen, and the new method is shown to identify these cases of substantial core–valence mixing. Finally,
even when there is limited core–valence mixing, the frozen-core approximation can introduce errors of more than 5 kcal/mol,
which is much larger than the presumed accuracy of models such as G2 and CBS-QB3. The source of these errors includes interatomic
core–core and core–valence dispersion forces.
Received: 31 August 2001 / Accepted: 11 October 2001 / Published online: 9 January 2002 相似文献
17.
For the 54 atoms from H to Xe, compact yet accurate segmented Gaussian-type basis sets have been constructed for all electron
calculations. Non-relativistic nZP (Sapporo-nZP) sets for Li–Xe and relativistic nZP (Sapporo-DK-nZP) sets for K–Xe are developed (n = D, T, Q), which efficiently incorporate valence and core electron correlations. Test calculations at the coupled-cluster
level of theory are performed for spectroscopic constants of 12 hydrides of s- and d-block atoms and 12 diatomics of p-block atoms in their ground states. For all molecules, the calculated spectroscopic constants approach to the experimental
values smoothly as the basis set quality increases. 相似文献
18.
Relativistic energy-consistent small-core lanthanide pseudopotentials of the Stuttgart–Bonn variety and extended valence
basis sets have been used for the investigation of the dimers La2 and Lu2. It was found that the ground states for La2 and Lu2 are most likely 1∑
g
+ (σ
g
2π
u
4) and 3∑
g
− (4f
144f
14σ
g
2σ
u
2πu
2), respectively. The molecular constants including error bars were derived from multireference configuration interaction as
well as coupled-cluster calculations, taking into account corrections for atomic spin–orbit splitting as well as possible
basis set superposition errors. The theoretical values for La2 (R
e=2.70±0.03 ?, D
e=2.31±0.13 eV, ωe=186±13 cm−1) show good agreement with the experimental binding energy (D
e=2.52±0.22 eV), but the experimental vibrational constant in an Ar matrix (ωe=236±0.8 cm−1) is significantly higher. For Lu2 the theoretical values (R
e=3.07±0.03 ?, D
e=1.40±0.12 eV, ωe=123±1 cm−1) are in overall excellent agreement with experimental data (D
e=1.43±0.34 eV, ωe=122± 1 cm−1). The electronic structures of La2 and Lu2 are compared to those other lanthanide dimers and trends in the series are discussed.
Received: 25 March 2002 / Accepted: 2 June 2002 / Published online: 21 August 2002 相似文献
19.
Kenneth G. Dyall 《Theoretical chemistry accounts》2002,108(6):365-365
The coefficients of the atomic Foldy-Wout-huysen transformed large component, which can be used in scalar relativistic calculations,
are provided in an internet archive for the relativistic double zeta basis sets for the 4p, 5p and 6p elements previously published by the author.
Published online: 14 November 2002
Correspondence to: K.G. Dyall e-mail: dyall@schrodinger.com 相似文献
20.
Computational schemes are presented with which to evaluate the electrostatic Coulomb energy in relativistic molecular electronic
structure calculations using a basis of four-component Dirac spinor amplitudes. We demonstrate that algorithms may be constructed
and implemented which differ only in minor details from those in common use in nonrelativistic quantum chemistry, and that
the four-component formalism is neither as complicated nor as expensive as has been suggested recently in the literature.
Spherically symmetrical atomic basis sets are presented which indicate that accurate representations of the Coulomb energy
may be obtained using modest expansions of the electronic density in a scalar auxiliary basis set of spherical harmonic Gaussian-type
functions.
Received: 15 April 2002 / Accepted: 15 May 2002 / Published online: 29 July 2002 相似文献