Papers by Demetrios Xenides
(Hyper)polarizability dependence on the interatomic distance of N4 (Td): Fourth order polynomials and third order derivatives
Journal of Molecular Structure: THEOCHEM, 2006
On the performance of DFT methods in (hyper)polarizability calculations: N4 (Td) as a test case
Journal of Molecular Structure: THEOCHEM, 2007
We present an extensive study of the electric (hyper)polarizabilities of N 4 using conventional a... more We present an extensive study of the electric (hyper)polarizabilities of N 4 using conventional ab initio techniques, up to the couple cluster approach [CCSD(T)], and Density Functional Theory (DFT) methods. We evaluate the relative performance of the later by introducing graph ...
Fuzzy Neural Classifiers for Multi-Wavelength Interdigital Sensors
The use of multi-wavelength interdigital sensors for non-destructive testing is based on the capa... more The use of multi-wavelength interdigital sensors for non-destructive testing is based on the capability of the measuring system to classify the measured impendence according to some physical properties of the material under test. By varying the measuring frequency and the wavelength of the sensor (and thus the penetration depth of the electric field inside the material under test) we can
Combined experimental and theoretical treatment of the dipole polarizability of P_{4} clusters
Physical Review A, 2000
... Phys. Lett. 157, 479 (1987) [INSPEC][CAS]. J. Paldus and X. Li, Adv. Chem. Phys. 110, 1 (1999... more ... Phys. Lett. 157, 479 (1987) [INSPEC][CAS]. J. Paldus and X. Li, Adv. Chem. Phys. 110, 1 (1999) [CrossRef][CAS]. ... Phys. Lett. 156, 87 (1989) [INSPEC][CAS]. G. Maroulis, electronic mail addressmarou@upatras.gr. A. Schäfer, C. Huber, and R. Ahlrichs, J. Chem. Phys. ...
Multi-surface Pattern Separation of Interdigital Dielectrometry Data for Volume Detection
The use of multi-wavelength interdigital sensors for non-destructive testing is based on the capa... more The use of multi-wavelength interdigital sensors for non-destructive testing is based on the capability of the measuring system to classify the measured impendence according to some physical properties of the material under test. This is done mostly with computational techniques since the inverse problem is ill-posed and sometimes leads to physical unaccepted solutions. Thus, the successful application of interdigital sensors are related to the construction of a set of measurements sufficient to classify the physical property of interest. A separable measuring data set consists of measurements obtained in a predefined set of M-sensor wavelengths (multiples of a base wavelength) and in a predefined set of N-frequencies. The classification of the M×N-dimensional vectors obtained in this way can be used to detect volumes of different shapes and sizes inside a uniform medium. The multi-surface pattern separation techniques has been applied, showing that the detection of a volume is poss...
Journal of Statistical Mechanics: Theory and Experiment, 2008
Living communities can be considered as complex systems, thus a fertile ground for studies relate... more Living communities can be considered as complex systems, thus a fertile ground for studies related to their statistics and dynamics. In this study we revisit the case of the rhythmic applause by utilizing the model proposed by Vázquez et al. [A. Vázquez et al., Phys. Rev. E 73, 036127 (2006)] augmented with two contradicted driving forces, namely: Individuality and Companionship.
Electric polarizability and hyperpolarizability of BrCl(X 1 Σ + )
Journal of Physics B: Atomic, Molecular and Optical Physics, 2006
Trends of the bonding effect on the performance of DFT methods in electric properties calculations: A pattern recognition and metric space approach on some XY 2 (X = O, S and Y = H, O, F, S, Cl) molecules
Journal of Computational Chemistry, 2009
A test set of 10 molecules (open and ring forms of ozone and sulfur dioxide as well as water and ... more A test set of 10 molecules (open and ring forms of ozone and sulfur dioxide as well as water and hydrogen sulfide and their respective fluoro- and chloro-substituted analogs) of specific atmospheric interest has been formed as to assess the performance of various density functional theory methods in (hyper)polarizability calculations against well-established ab initio methods. The choice of these molecules was further based on (i) the profound change in the physics between isomeric systems, e.g., open (C(2v)) and ring (D(3h)) forms of ozone, (ii) the relation between isomeric forms, e.g., open and ring form of sulfur dioxide (both of C(2v) symmetry), and (iii) the effect of the substitution, e.g., in fluoro- and chloro-substituted water analogs. The analysis is aided by arguments chosen from the information theory, graph theory, and pattern recognition fields of Mathematics: In brief, a multidimensional space is formed by the methods which are playing the role of vectors with the independent components of the electric properties to act as the coordinates of these vectors, hence the relation between different vectors (e.g., methods) can be quantified by a proximity measure. Results are in agreement with previous studies revealing the acceptable and consistent behavior of the mPW1PW91, B3P86, and PBE0 methods. It is worth noting the remarkable good performance of the double hybrid functionals (namely: B2PLYP and mPW2PLYP) which are for the first time used in calculations of electric response properties.
Dipole, dipole–quadrupole, and dipole–octopole polarizability of adamantane, C[sub 10]H[sub 16], from refractive index measurements, depolarized collision-induced light scattering, conventional ab initio and density functional theory calculations
The Journal of Chemical Physics, 2001
Refractive index (RI) measurements, depolarized collision-induced light (CILS) scattering and ab ... more Refractive index (RI) measurements, depolarized collision-induced light (CILS) scattering and ab initio quantum chemical calculations are used to determine the dipole (alpha), dipole-quadrupole (A), and dipole-octopole polarizability (E) of adamantane, C10H16. For this molecule of symmetry group Td the three polarizabilities can be represented by a single scalar quantity. From experiment we obtain for the static dipole polarizability at T~400-500
The Journal of Chemical Physics, 2008
The dependences of the static dipole polarizabilities per atom ͑PPAs͒ on the bonding and shape of... more The dependences of the static dipole polarizabilities per atom ͑PPAs͒ on the bonding and shape of selected stoichiometric aluminum phosphide clusters ͑ground states and higher lying species͒ of small and medium sizes have been comprehensively studied at Hartree-Fock and the second order Møller-Plesset perturbation levels of theory. It is shown that the nonmonotonic size variations in the mean PPAs of AlP species which maintain closed cagelike structures, frequently observed in clusters, are directly related to covalent homoatomic bonds inside each cluster's framework. Accordingly, the PPAs of clusters which are characterized by one or more bonds between the Al and P atoms are larger than the PPAs of clusters with the uniform alternating Al-P bond matrix. This is caused by the electron transfer increase from the electropositive Al to the electronegative P atom with the cluster growth. This transfer is larger for the clusters characterized by alternating Al-P bonding. The later effect explains the decrease in the PPA of AlP species which maintain closed cage-like structures, with the cluster growth. However, this picture drastically changes for artificial metastable prolate species built up by the ground states of smaller clusters. It is demonstrated that for prolate binary AlP clusters of medium size, the shape dominates against any other structural or bonding factor, forcing the PPA to increase with the cluster size. Nonetheless, as the cluster size grows, it is predicted that the PPAs of the studied prolate clusters will saturate eventually with the cluster size. Also, it is verified that the theoretical predicted polarizabilities of AlP semiconductor clusters are larger than the bulk polarizability in accord with other theoretical predictions for similar systems. Lastly, it is pointed out that major bonding or structural changes should take place in order the convergence with the bulk polarizability to be accomplished since it is revealed that the size increase is a necessary but not a sufficient factor for the cluster to bulk transition.
Computational and Theoretical Chemistry, 2012
We have obtained the electric quadrupole and hexadecapole moment, dipole polarizability and hyper... more We have obtained the electric quadrupole and hexadecapole moment, dipole polarizability and hyperpolarizability of copper tetramer from finite-field ab initio and density functional theory (DFT) calculations performed with a systematic sequence of basis sets built upon the Stevens/Basch/Krauss effective core potential triple-split basis set CEP-121G. Our present ab initio values show significant discrepancies with previous all-electron results [G. Maroulis, A. Haskopoulos, J. Comput. Theor. Nanosci. 6 (2009) 418]. Representative calculations yield self-consistent field (SCF) values (second-order Møller-Plesset results in parentheses) for (hyper)polarizability invariants: mean polarizability ⇑ Corresponding author.
Chemical Physics Letters, 2008
The mean dipole polarizabilities and the polarizability anisotropies of stoichiometric Al n P n (... more The mean dipole polarizabilities and the polarizability anisotropies of stoichiometric Al n P n (n = 2-9) clusters are investigated and presented for the first time. Basis set augmentation effects on the 6-31+G substrate are studied and discussed. The electron correlation contributions to the polarizability were studied for clusters up to 12 atoms at MP2 and CCSD(T) levels of theory, and the performance of the widely used B3LYP, B3PW91, mPW1PW91 functionals are assessed. From the methodological standpoint, our results show that for clusters where the ionic contribution to the bonding is strong the MP2 method yields polarizability values in very good agreement with the more accurate CCSD(T) approximation.
Chemical Physics Letters, 2010
A critical analysis of the performance of new generation functionals on the calculation of the (h... more A critical analysis of the performance of new generation functionals on the calculation of the (hyper) polarizabilities of clusters of varying stoichiometry: Test case the SimGen a b s t r a c t
We have calculated the static dipole polarizabilities of stoichiometric AlnPn clusters with n = 2... more We have calculated the static dipole polarizabilities of stoichiometric AlnPn clusters with n = 2-9 at HF, B3LYP, B3PW91 and mPW1PW91 levels of theory using basis sets of increasing size. Our results show that AIP clusters behave like the well studied GaAs clusters and their per-atom polarizabilities decrease rapidly with cluster size. At HF and the DFT levels the per-atom-mean
Computational Quantum Chemistry: From Atoms and Molecules to Clusters and Nano‐objects
This symposium on Computational Quantum Chemistry attracted 36 papers and included a special sess... more This symposium on Computational Quantum Chemistry attracted 36 papers and included a special session on electric polarizability.
Accurate values for the dipole polarizability of the cyclic form of ozone have been obtained from... more Accurate values for the dipole polarizability of the cyclic form of ozone have been obtained from finite-field many-body perturbation theory and coupled-cluster calculations. Our best effort yields near-Hartree-Fock values of 16.09 and −9.12 e 2 a 2 0 E −1 h for the mean value (ᾱ) and the anisotropy ( α) of the dipole polarizability. Electron correlation increasesᾱ by only a few per cent but has a stronger effect on α. Our CCSD(T) values, obtained with a [9s6p5d1f] basis set, areᾱ = 16.48 and α = −6.79 e 2 a 2 0 E −1 h . Thus, the cyclic form is less polarizable than the open one which is characterized by a mean polarizability ofᾱ = 18.95 e 2 a 2 0 E −1 h (Maroulis G 1994 J. Chem. Phys. 101 4949).
How does protonation affect the electron density of ozone
Molecular Physics, 2002
Journal of Physical Chemistry A, 2003
We have obtained electric properties of PtP from finite-field Møller-Plesset perturbation theory,... more We have obtained electric properties of PtP from finite-field Møller-Plesset perturbation theory, density functional theory and coupled cluster techniques. Reference, near-Hartree-Fock values have been obtained with a very large (20s15p10d5f) uncontracted basis set consisting of 300 Gaussian-type functions. At the experimental equilibrium bond length of R e ) 1.8934 Å we obtain self-consistent field values of 1.0682 ea 0 2 for the quadrupole moment (Θ), -41.68 ea 0 4 for the hexadecapole moment (Φ), 51.16 for the mean (R) and 28.58 e 2 a 0 2 E h -1 for the anisotropy of the dipole polarizability, and 16.5 × 10 3 e 4 a 0 4 E h -3 for the mean second dipole hyperpolarizability (γ). Electron correlation reduces strongly the magnitude of the electric moments. Both components of the dipole polarizability are reduced by electron correlation, but a small increase is observed for the dipole hyperpolarizability. Our best post-Hartree-Fock values have been obtained with a [9s7p5d3f] basis set at the CCSD(T) level of theory: Θ ) 0.4850 ea 0 2 , Φ ) -31.25 ea 0 4 , R ) 49.20 and ∆R ) 28.02 e 2 a 0 2 E h -1 , γ ) 16.8 × 10 3 e 4 a 0 4 E h -3 . The bond-length dependence around R e has been obtained for all properties. Conventional density functional theory methods predict dipole polarizabilities close enough to the most accurate CCSD(T) values but overestimate the second dipole hyperpolarizability. The mean dipole polarizability changes as R(NaK) > R(AlCl) > R(SiS) > R(P 2 ) > R(Zn) for some isoelectronic, 30-electron systems. It is seen that the electric properties in the sequence N 2 fP 2 fAs 2 display regular changes.
Chemical Physics Letters, 2000
Accurate values are reported for the static hyperpolarizability of SO . We have obtained near-Har... more Accurate values are reported for the static hyperpolarizability of SO . We have obtained near-Hartree-Fock SCF values 2 2 2 y1
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Papers by Demetrios Xenides