Matus Milko - Academia.edu (original) (raw)

Papers by Matus Milko

Microscopy conference 2009, 2009

Note: dvanced functional materials – Science and technology of sp2 carbon allotropes, Symposium O... more Note: dvanced functional materials – Science and technology of sp2 carbon allotropes, Symposium O Reference CIME-PRESENTATION-2010-002 Record created on 2010-02-16, modified on 2017-05-12

Journal of electron spectroscopy and related phenomena, 2014

Here we report on a combined experimental and theoretical study on the structural and electronic ... more Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (k x k y )-maps using angle-resolved photoelectron spectroscopy with theoretical momentum maps of the free molecule's highest occupied molecular orbital (HOMO). This structural information is confirmed by total energy calculations within the framework of van-der-Waals corrected density functional theory. The electronic structure is further analyzed by computing the molecule-projected density of states, using both a semi-local and a hybrid exchange-correlation functional. In agreement with experiment, the HOMO is located about 1.2 eV below the Fermi-level, while there is no significant char...

Zeitschrift für anorganische und allgemeine Chemie, 2003

... we propose the opti-mum pressure region for the synthesis of ternary silicon oxynitride and a... more ... we propose the opti-mum pressure region for the synthesis of ternary silicon oxynitride and a ... of the structures indicated a mapping of N and O onto the anion sites is ... The ordering of vacancies causes appreciable atomic displacements and a symmetry reduction from Fd3¯m, the ...

Small, 2011

Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Physical Review B, 2012

We provide a simple scheme for predicting the electronic structure of van-der-Waals bound systems... more We provide a simple scheme for predicting the electronic structure of van-der-Waals bound systems, based on the mere knowledge of the electronic structure of the subunits. We demonstrate this with the example of nano-peapods, consisting of polythiophene encapsulated in single-wall carbon nanotubes. Using density functional theory we disentangle the contributions to the level alignment. The main contribution is shown to be given by the ionization potential of the polymer inside the host, which, in turn is determined by the curvature of the tube. Only a small correction arises from charge redistributions within the domains of the constituents. Polarization effects turn out to be minor due to the cylindrical geometry of the peapods and their dielectric characteristics. Our findings open a perspective towards designing opto-electronic properties of such complex materials.

Physical Review B, 2011

Stability and structural properties of nanopeapods are investigated by means of density-functiona... more Stability and structural properties of nanopeapods are investigated by means of density-functional theory (DFT) including van der Waals interactions. As a prototypical system of organic π-conjugated molecules embedded into single-wall carbon nanotubes, we study benzene inside zigzag nanotubes (n,0), with n ranging from 10 to 18. We explore the position and orientation of the molecule inside the cavity and find the optimal tube diameter for encapsulation to be around 1 nm. We compute that, overall, the molecule tends to align its molecular plane parallel to the tube axis. The internal orientation and molecule-wall distance depend, however, quite strongly on the tube diameter. The overall energy minimum is found for a situation in which the benzene ring takes a tilted position inside the (13,0) nanotube. Chirality turns out not to play a role in terms of the energetics. When benzene arrays are confined in nanotubes, the intermolecular distances can differ from those in the gas phase. Intermolecular interactions are important and further stabilize the peapods. As these as well as the molecule-tube interactions are governed by dispersive forces, we critically assess the performance of different DFT-based methods in this respect. Comparing four different computational schemes including both ab initio and semi-empirical treatment of van der Waals interactions, we conclude that vdW-DF is most reliable in terms of energetics and structural properties of these hybrids.

Microscopy and Microanalysis, 2009

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia... more Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

The Journal of Physical Chemistry Letters, 2013

The Journal of Chemical Physics, 2006

Density fitting approach to Coulomb integrals for infinite systems with translational periodicity... more Density fitting approach to Coulomb integrals for infinite systems with translational periodicity is reformulated in direct space. Despite of the Coulomb infinite decay of some integrals, direct-space calculation is shown to be feasible. Moreover, we show that the direct-space ansatz is completely equivalent to our previous formulation in reciprocal space. Computational demands scale linearly with the number of unit cells. In addition, direct-space treatment has some practical advantages over the reciprocal-space formulation. The efficiency of our scheme is demonstrated on systems with translational periodicity in one dimension. Computation time takes only a small fraction of the conventional calculation with exact integrals. We show that for infinite systems auxiliary basis sets of equally good quality as for molecules can be constructed in a systematic way.

International Journal of Quantum Chemistry, 2007

ABSTRACT Recently implemented approach to treat the two-electron (Coulomb) integrals in periodic ... more ABSTRACT Recently implemented approach to treat the two-electron (Coulomb) integrals in periodic systems via density fitting has been examined using Hartree--Fock calculations for model systems including trans-polyacetylene, poly(methineimine), and trans-polycyanoborane. At the moment, the exchange part of the Fock operator has been taken exact. In addition to total energies, the performance has been assessed for electron densities, main parameters of the band structure as well as for the topology of selected important bands. DZP and 6-31G** atomic orbital basis sets were combined with different auxiliary sets including standard ones optimized for molecules. For the purpose of systematic comparisons also auxiliary bases based on the correlation consistent cc-pVXZ and cc-pCVXZ hierarchies have been examined. Though these hierarchies were not designed for density fitting they perform fairly well, too, exhibiting an exponential convergence behavior with the increasing cardinal number. It is shown that for bands of chemical interest the band structure is well reproduced even with quite small auxiliary sets. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

International Journal of Quantum Chemistry, 2005

A formulation of MP2-R12 theory is presented leading to simplified matrix elements in the R12 par... more A formulation of MP2-R12 theory is presented leading to simplified matrix elements in the R12 part. The resulting formulas are free from the integrals over the commutator of the kinetic operator with inter-electronic distance, which means a substantial decreasing of the computational demands. The use of an auxiliary basis set for the resolution of identity is discussed. First results using the standard approximation are compared with the former variants of MP2-R12 for CH 2 , CH 4 , NH 3 , H 2 O, HF, CO, CH 3 OH, N 2 , and F 2. The results show that the new formulation is not only less demanding, but also preferred concerning the convergence properties toward the basis set limit.

ABSTRACT Nanohybrids i. e. single wall carbon nanotubes with encapsulated organic molecules have ... more ABSTRACT Nanohybrids i. e. single wall carbon nanotubes with encapsulated organic molecules have been proposed for opto-electronic devices as they combine the unique mechanical and electronic properties of nanotubes with the desired optical properties of π-conjugated molecules. We investigate structural, cohesive and optical properties of these hybrid systems using density functional theory. Including the contributions for the non-local dispersive interactions, we examine in a systematic manner the effect of tube diameter and chirality on the stability and bonding characteristics of the peapod as well as the position of the molecule inside the tube. We find that these systems are almost exclusively van-der-Waals bound. Based on a series of oligo-thiophenes encapsulated into zig-zag nanotubes, we explore how the presence of the molecules inside the cavity can alter the electronic and optical properties. In particular, we inspect new features in the dielectric and loss functions due to transitions between the states of the molecule and the nanotube.