R. Nieminen
Aalto University, Department of Applied Physics, Faculty Member
- Computational condensed-matter and materials physicist.edit
ABSTRACT We present an extensive study of the structure and energetics of monovacancies and antisites in InP. Using a first-principles approach, the different charge states of indium and phosphorus vacancies and antisites are examined.... more
ABSTRACT We present an extensive study of the structure and energetics of monovacancies and antisites in InP. Using a first-principles approach, the different charge states of indium and phosphorus vacancies and antisites are examined. The lattice distortions around the defects are derived fully self-consistently with respect to both electronic and ionic degrees of freedom. Jahn-Teller relaxations, defect induced one-electron energy levels and ionization potentials in the band gap are discussed. From the formation energies, we predict the favored vacancies and antisites under different stoichiometry conditions.
Research Interests:
Research Interests:
... Vacancy-type defect distributions near argon sputtered Al(100) surface studied by variable-energy positrons and molecular dynamics simulations. J. Mäkinen a , A. Vehanen a , P. Hautojärvi a , H. Huomo a , J. Lahtinen a , RM Nieminen b... more
... Vacancy-type defect distributions near argon sputtered Al(100) surface studied by variable-energy positrons and molecular dynamics simulations. J. Mäkinen a , A. Vehanen a , P. Hautojärvi a , H. Huomo a , J. Lahtinen a , RM Nieminen b and S. Valkealahti b. ...
Research Interests:
Research Interests:
We report on our work with vibrational absorption, vibrational circular dichroism, Raman scattering, Raman optical activity, and surface‐enhanced Raman spectroscopy to study protein and DNA structure, hydration, and the binding of... more
We report on our work with vibrational absorption, vibrational circular dichroism, Raman scattering, Raman optical activity, and surface‐enhanced Raman spectroscopy to study protein and DNA structure, hydration, and the binding of ligands, drugs, pesticides, or herbicides via a combined theoretical and experimental approach. The systems we have studied systematically are the amino acids (L‐alanine, L‐tryptophan, and L‐histidine), peptides (N‐4271 acetyl L‐alanine N′‐methyl amide, N‐acetyl L‐tryptophan N′‐methyl amide, N‐acetyl L‐histidine N′‐methyl amide, L‐alanyl L‐alanine, tri‐L‐serine, N‐acetyl L‐alanine L‐proline L‐tyrosine N′‐methyl amide, Leu‐enkephalin, cyclo‐(gly‐L‐pro)3, N‐acetyl (L‐alanine)n N′‐methyl amide), 3‐methyl indole, and a variety of small molecules (dichlobenil and 2,6‐dochlorobenzamide) of relevance to the protein systems under study. We have used molecular mechanics, the SCC‐DFTB, SCC‐DFTB+disp, RHF, MP2, and DFT methodologies for the modeling studies with the ...
Research Interests: Chemistry, Computational Chemistry, Quantum Chemistry, Cancer Research, Chemical Physics, and 15 moreMolecular Mechanics, Complex System, Density Functional Theory, Electronic properties, Hydration, DNA Structure, Physik, Biomolecule, DDC, Amino Acid Profile, Alanine, Raman Scattering, Experimental Measurement, Molecule, and Raman Optical Activity
Research Interests:
Research Interests:
The annihilation characteristics of a positron trapped in spherical clusters of 1., 50 vacancies in Al and Mo are calculated. The results are found to depend sensitively on the void size up to a radius of about 5 Å, beyond which the size... more
The annihilation characteristics of a positron trapped in spherical clusters of 1., 50 vacancies in Al and Mo are calculated. The results are found to depend sensitively on the void size up to a radius of about 5 Å, beyond which the size dependence disappears. The residual resistivity is shown to be nearly independent of the microvoid size during initial
Research Interests:
Research Interests:
The workshop “Atomic structure of nanosystems from first-principles simulations and microscopy experiments” took place on a ship going from Helsinki to Stockholm and back on May 15-17, 2012 . The workshop was attended by 47 participants... more
The workshop “Atomic structure of nanosystems from first-principles simulations and microscopy experiments” took place on a ship going from Helsinki to Stockholm and back on May 15-17, 2012 . The workshop was attended by 47 participants (including the organizers) from all over the world. The financial support from the Psi-K network with additional support from the COST Action MP0901 NanoTP, the National Graduate School in Materials Physics and Academy of Finland made it possible to invite a considerable number of world-renowned experts in the computational materials science and nanoscience and, at the same time, minimize the accommodation expenses for students and young researchers.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT The positron states in the perfect GaAs lattice and at fully relaxed vacancies with different total charges have been calculated. Moreover, the metastable configuration of the As anti-site in GaAs proposed as a model for the EL2... more
ABSTRACT The positron states in the perfect GaAs lattice and at fully relaxed vacancies with different total charges have been calculated. Moreover, the metastable configuration of the As anti-site in GaAs proposed as a model for the EL2 defect is considered. The atomic structures of the defects are taken from recent ab initio molecular dynamics calculations. The positron states and the ensuing positron annihilation rates and trap binding energies have been determined by the method based on the superposition of atomic electron densities. A comparison of the results with experimental data shows that, while the present theoretical approach gives a consistent and qualitative interpretation, it fails to reproduce the trapped state lifetimes quantitatively. It is shown that a localized positron can affect the lattice relaxations around the defect. Therefore, it is suggested that the positron should be treated fully self-consistently, simultaneously with electrons, in the ab initio molecular dynamics in order to determine the way in which the localized positron affects the electron structure and ionic relaxation near the vacancy.
Research Interests:
We have developed a detailed mathematical model and numerical simulation tools based on the streamline upwind/Petrov-Galerkin (SUPG) finite element formulation for the Czochralski silicon crystal growth. In this paper we consider the... more
We have developed a detailed mathematical model and numerical simulation tools based on the streamline upwind/Petrov-Galerkin (SUPG) finite element formulation for the Czochralski silicon crystal growth. In this paper we consider the mathematical modeling and numerical simulation of the time-dependent melt flow and temperature field in a rotationally symmetric crystal growth environment. Heat inside the Czochralski furnace is transferred by