Records |
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Elusive s-f intrasite interactions and double exchange in solids: ferromagnetic versus nonmagnetic ground state |
Type |
A1 Journal article |
Year |
2009 |
Publication |
Journal of experimental and theoretical physics |
Abbreviated Journal |
J Exp Theor Phys+ |
Volume |
109 |
Issue |
2 |
Pages |
286-292 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
From the theory of many-electron states in atoms, we know that there exists a strong Coulomb repulsion, which results in the electronic term structure of atoms and is responsible for Hunds rules. By expanding the Coulomb on-site repulsion into a multipolar series, we derive this interaction and show that it is also present in solids as a correlation effect, which means that the interaction requires a multideterminant version of the Hartree-Fock method. Of particular interest is the case where this interaction couples states of localized ( f) and delocalized ( s) electrons. We show that the interaction is bilinear in the creation/annihilation operators for localized electrons and bilinear in the operators for conduction electrons. To study the coupling, we consider a simple model in the framework of an effective limited configuration interaction method with one localized f-electron and one itinerant s-electron per crystal site. The on-site multipole interaction between the f- and s-electrons is explicitly taken into account. It is shown that depending on the low-lying excitation spectrum imposed by the crystal electric field, the model can lead not only to ferromagnetism but also to a nonmagnetic state. The model is relevant for solids with localized and itinerant electron states. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
Woodbury, N.Y. |
Editor |
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Language |
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Wos |
000270506500014 |
Publication Date |
2009-09-18 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1063-7761;1090-6509; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
1.196 |
Times cited |
3 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 1.196; 2009 IF: 0.871 |
Call Number |
UA @ lucian @ c:irua:79163 |
Serial |
1027 |
Permanent link to this record |
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|
|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Ab initio approach to superexchange interactions in alkali doped fullerides AC60 |
Type |
P1 Proceeding |
Year |
2004 |
Publication |
AIP conference proceedings
T2 – 18th International Winterschool/Euroconference on Electronic Properties, of Novel Materials, MAR 06-JUN 13, 2004, Kirchberg, AUSTRIA |
Abbreviated Journal |
|
Volume |
|
Issue |
|
Pages |
393-396 |
Keywords |
P1 Proceeding; Condensed Matter Theory (CMT) |
Abstract |
The superexchange interactions between the fullerenes arise as a result of the electron transfer from the C-60 molecule to the alkali atom and back. We present a scheme, which is a configuration interaction approach based on the valence bond (Heitler-London) method. The effect of superexchange is described together with chemical bonding by constructing and solving a secular equation, rather than by using a perturbation treatment. We have considered 180degrees and 90degrees superexchange for the C-60 Cs-C-60 pathways. The calculations account for unusual electronic properties of polymer orthorhombic and quenched cubic phases of CsC60: two lines in nuclear magnetic resonance experiments, the development of a spin-singlet ground state and a decrease of magnetic susceptibility as T-->0. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York |
Editor |
|
Language |
|
Wos |
000224699400085 |
Publication Date |
2004-11-11 |
Series Editor |
|
Series Title |
|
Abbreviated Series Title |
|
Series Volume |
723 |
Series Issue |
|
Edition |
|
ISSN |
0-7354-0204-3 |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
|
Times cited |
|
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: NA |
Call Number |
UA @ lucian @ c:irua:103752 |
Serial |
27 |
Permanent link to this record |
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Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Electric quadrupole interactions and the γ-α phase transition in Ce: the role of conduction electrons |
Type |
A1 Journal article |
Year |
2000 |
Publication |
European physical journal : B : condensed matter and complex systems |
Abbreviated Journal |
Eur Phys J B |
Volume |
17 |
Issue |
|
Pages |
15-32 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
|
Address |
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Corporate Author |
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Thesis |
|
Publisher |
|
Place of Publication |
Berlin |
Editor |
|
Language |
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Wos |
000089339900004 |
Publication Date |
2003-05-15 |
Series Editor |
|
Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1434-6028; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
1.461 |
Times cited |
8 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 1.461; 2000 IF: 2.077 |
Call Number |
UA @ lucian @ c:irua:34338 |
Serial |
888 |
Permanent link to this record |
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|
|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Electronic structure and electric quadrupoles of a polymerized chain in solid AC60 |
Type |
A1 Journal article |
Year |
2001 |
Publication |
Solid state communications |
Abbreviated Journal |
Solid State Commun |
Volume |
117 |
Issue |
|
Pages |
739-743 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
|
Address |
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Corporate Author |
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Thesis |
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Publisher |
|
Place of Publication |
New York, N.Y. |
Editor |
|
Language |
|
Wos |
000167538300010 |
Publication Date |
2002-07-25 |
Series Editor |
|
Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0038-1098; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
1.554 |
Times cited |
10 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 1.554; 2001 IF: 1.381 |
Call Number |
UA @ lucian @ c:irua:36881 |
Serial |
1009 |
Permanent link to this record |
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|
|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Many electron- and hole terms of molecular ions C60n\pm |
Type |
A1 Journal article |
Year |
2003 |
Publication |
Coupling In Chemistry And Physics |
Abbreviated Journal |
Adv Quantum Chem |
Volume |
44 |
Issue |
|
Pages |
305-312 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
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Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York, N.Y. |
Editor |
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Language |
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Wos |
000188940800019 |
Publication Date |
2004-05-19 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0065-3276; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
1.196 |
Times cited |
1 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 1.196; 2003 IF: 0.375 |
Call Number |
UA @ lucian @ c:irua:104131 |
Serial |
1942 |
Permanent link to this record |
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|
|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Microscopic theory of quadrupolar oredring in TmTe |
Type |
A1 Journal article |
Year |
2001 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
63 |
Issue |
|
Pages |
1-10 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
|
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
Lancaster, Pa |
Editor |
|
Language |
|
Wos |
000167402100025 |
Publication Date |
2002-07-27 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
0163-1829;1095-3795; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
7 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 3.836; 2001 IF: NA |
Call Number |
UA @ lucian @ c:irua:36882 |
Serial |
2033 |
Permanent link to this record |
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|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Microscopic theory of the rhombohedral phase and transition to the monoclinic phase of solid C70 |
Type |
A1 Journal article |
Year |
1996 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
54 |
Issue |
18 |
Pages |
12733-12743 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Starting from a model of microscopic interactions between C-70 molecules, we have developed a theory which describes the orientational dynamics and its coupling to lattice displacements in the rhombohedral phase of C-70 fullerite. The Landau free energy is calculated. We obtain a first-order phase transition to a monoclinic structure with the space group P2(1)/m. The transition is driven by the condensation of orientational quadrupoles at the F point of the Brillouin zone of the rhombohedral lattice. We find no evidence that the monoclinic structure is connected with the freezing in of orientations around the fivefold molecular axis. We calculate the lattice strains that are associated with the transition to the monoclinic structure. The theory is compared with a range of experimental data on the phase transition. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
Lancaster, Pa |
Editor |
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Language |
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Wos |
A1996VT68200028 |
Publication Date |
2002-07-27 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
|
ISSN |
0163-1829;1095-3795; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.736 |
Times cited |
5 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
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Approved |
no |
Call Number |
UA @ lucian @ c:irua:16357 |
Serial |
2034 |
Permanent link to this record |
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|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Molecular terms and optical transitions of C60n+/- molecular ions |
Type |
P1 Proceeding |
Year |
2002 |
Publication |
AIP conference proceedings
T2 – 16th International Winterschool on Electronic Properties of Novel, Materials, MAR 02-09, 2002, KIRCHBERG, AUSTRIA |
Abbreviated Journal |
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Volume |
|
Issue |
|
Pages |
417-420 |
Keywords |
P1 Proceeding; Condensed Matter Theory (CMT) |
Abstract |
We have studied the molecular energy terms of the hole configurations (h(u)(+))(m), m=2,3,4,5 of C-60(m+) cations and the electronic configurations (t(1u))(n) n=2,3,4, as well as (t(1u))(n-1)t(1g) of the C-60(n-) anions. The lowest terms (within an energy span of 0.03 eV) for C-60(2+) are three triplets T-3(1g), (3)G(g), T-3(2g) and for C-60(3+) are three quartets T-4(1u), (4)G(u), T-4(2u), which favor Jahn-Teller distortions. For the ground state of C-60(2-) we find a triplet T-3(1g) in agreement with Hund's rules. Our method takes into account intramolecular direct and exchange multipolar Coulomb interactions. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York |
Editor |
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Language |
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Wos |
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Publication Date |
0000-00-00 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
633 |
Series Issue |
|
Edition |
|
ISSN |
0-7354-0088-1 |
ISBN |
|
Additional Links |
UA library record; WoS full record; |
Impact Factor |
|
Times cited |
|
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: NA |
Call Number |
UA @ lucian @ c:irua:103905 |
Serial |
2187 |
Permanent link to this record |
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|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Quantum charge density fluctuations and the γ-α phase transition in Ce |
Type |
A1 Journal article |
Year |
1999 |
Publication |
European physical journal : B : condensed matter and complex systems |
Abbreviated Journal |
Eur Phys J B |
Volume |
9 |
Issue |
|
Pages |
619-634 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
|
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
Berlin |
Editor |
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Language |
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Wos |
000081615500009 |
Publication Date |
2002-08-25 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
|
Edition |
|
ISSN |
1434-6028; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
1.461 |
Times cited |
19 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 1.461; 1999 IF: 1.705 |
Call Number |
UA @ lucian @ c:irua:28504 |
Serial |
2774 |
Permanent link to this record |
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|
Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Superexchange and electron correlations in alkali fullerides AC60, A=K, Rb, Cs |
Type |
A1 Journal article |
Year |
2005 |
Publication |
The journal of chemical physics |
Abbreviated Journal |
J Chem Phys |
Volume |
122 |
Issue |
6 |
Pages |
064310-64314 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
Superexchange interactions in alkali fullerides AC(60) are derived for C-60 molecular ions separated by interstitial alkali-metal ions. We use a multiconfiguration approach which comprises the lowest molecular orbital states of the C-60 molecule and the excited s and d states of the alkali-metal atom A. Interactions are described by the valence bond (Heitler-London) method for a complex (C-60 – A – C-60) – with two valence electrons. The electronic charge transfer between the alkali-metal atom and a neighboring C-60 molecule is not complete. The occupation probability of excited d and s states of the alkali atom is not negligible. In correspondence with the relative positions of the C-60 molecules and A atoms in the polymer crystal, we consider 180degrees and 90degrees (angle) superexchange pathways. For the former case the ground state is found to be a spin singlet separated from a triplet at similar to20 K. For T < 20 K there appear strong spin correlations for the 180degrees superexchange pathway. The results are related to spin lattice relaxation experiments on CsC60 in the polymerized and in the quenched cubic phase. (C) 2005 American Institute of Physics. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
New York, N.Y. |
Editor |
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Language |
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Wos |
000226918100018 |
Publication Date |
2005-02-02 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
|
ISSN |
0021-9606; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
2.965 |
Times cited |
11 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
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Approved |
Most recent IF: 2.965; 2005 IF: 3.138 |
Call Number |
UA @ lucian @ c:irua:102740 |
Serial |
3377 |
Permanent link to this record |
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Author |
Nikolaev, A.V.; Michel, K.H. |
Title |
Symmetry lowering at the structural phase transitions in NpO2 and UO2 |
Type |
A1 Journal article |
Year |
2003 |
Publication |
Physical review : B : condensed matter and materials physics |
Abbreviated Journal |
Phys Rev B |
Volume |
68 |
Issue |
5 |
Pages |
054112-054112,7 |
Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
Abstract |
The structural phase transitions with electric-quadrupole long-range order in NpO2 (Fm (3) over barm-->Pn (3) over barm) and UO2 (Fm (3) over barm-->Pa (3) over bar) are analyzed from a group theoretical point of view. In both cases, the symmetry lowering involves three quadrupolar components belonging to the irreducible representation T-2g (Gamma(5)) of O-h and condensing in a triple-q structure at the X point of the Brillouin zone. The Pa (3) over bar structure is close to Pn (3) over barm, but allows for oxygen displacements. The Pa (3) over bar ordering leads to an effective electrostatic attraction between electronic quadrupoles while the Pn (3) over barm ordering results in a repulsion between them. It is concluded that the Pn (3) over barm structure can be stabilized only through some additional process such as strengthening of the chemical bonding between Np and O. We also derive the relevant structure-factor amplitudes for Pn (3) over barm and Pa (3) over bar, and the effect of domains on resonant x-ray scattering experiments. |
Address |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
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Editor |
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Language |
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Wos |
000185240100038 |
Publication Date |
2003-08-29 |
Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
|
Series Issue |
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Edition |
|
ISSN |
0163-1829;1095-3795; |
ISBN |
|
Additional Links |
UA library record; WoS full record; WoS citing articles |
Impact Factor |
3.836 |
Times cited |
15 |
Open Access |
|
Notes ![sorted by Notes field, descending order (down)](img/sort_desc.gif) |
|
Approved |
Most recent IF: 3.836; 2003 IF: NA |
Call Number |
UA @ lucian @ c:irua:94847 |
Serial |
3405 |
Permanent link to this record |