In a generalization of the latest achievements in this field, and as a pattern of massive applications, we present here the Jahn-Teller effect (JTE) and pseudo-JTE (PJTE) as general tools in the study of physical and chemical phenomena related to structural properties of polyatomic systems. We show that the JTE and PJTE are no more specific features of particular (rare) systems (as it was assumed earlier), but virtual properties of all molecular and solid state formations. They occur as a result of vibronic coupling that compensates for the error (inadequacy) introduced in semi-classical definitions of polyatomic configurations by their high-symmetry nuclear positions, thus appending the basic understanding of related phenomena with a new dimension. The implications of the JTE and PJTE in observable properties varies significantly, being especially strong in the states of electronic degeneracy or pseudodegeneracy, but they cannot be a priory fully excluded for any system. After the introductory sections we demonstrate some of the more recent results of the influence of these effects on the observables in physical and chemical phenomena, together with a wide range of applications. The latter are conventionally separated in three parts: intermediate states in chemical and photochemical reactions, manipulation of structural properties of polyatomic systems targeting the JTE and PJTE, and applications in materials science. The illustrative examples include the origin of sudden polarization in photochemical reactions, methods of planarization of puckered (buckled) two-dimensional systems, modification of crystal sublattices by targeting the JTE parameters, the defining role of JTE and PJTE in electronics and spintronics, the origin of ferroelectricity and multiferroicity, as well as a novel property of solids, orientational polarization, and its applications.
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Four modifications of the Jahn-Teller effects. The problem of observables: spin-orbit interaction, tunneling splitting, and orientational polarization of solids.
Phys Chem Chem Phys
January 2023
Department of Chemistry, University of Texas at Austin, Austin, TX, 78712, USA.
In a semi-review paper, we first show that Landau's fundamental idea of the origin of spontaneous symmetry breaking (SSB) in atomic matter due to electronic degeneracy, termed the Jahn-Teller effect (JTE) and further developed into the pseudo-JTE (PJTE), was appended recently with two more modifications, the hidden JTE (h-JTE) and hidden PJTE (h-PJTE). All four versions of JTEs are defined in the adiabatic approximation by their adiabatic potential energy surfaces (APES), which possess a common feature - the lack of a minimum in the high-symmetry configuration, thus confirming (and extending) the Landau idea of SSB. However, although serving as a qualitative indication of the SSB and consequent possible (virtual) properties of the system, the APES by themselves are not experimentally observable directly, and this important feature of JTEs is often ignored.
View Article and Find Full Text PDFJahn-Teller and Pseudo-Jahn-Teller Effects: From Particular Features to General Tools in Exploring Molecular and Solid State Properties.
Chem Rev
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Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
In a generalization of the latest achievements in this field, and as a pattern of massive applications, we present here the Jahn-Teller effect (JTE) and pseudo-JTE (PJTE) as general tools in the study of physical and chemical phenomena related to structural properties of polyatomic systems. We show that the JTE and PJTE are no more specific features of particular (rare) systems (as it was assumed earlier), but virtual properties of all molecular and solid state formations. They occur as a result of vibronic coupling that compensates for the error (inadequacy) introduced in semi-classical definitions of polyatomic configurations by their high-symmetry nuclear positions, thus appending the basic understanding of related phenomena with a new dimension.
View Article and Find Full Text PDFBond-length distributions for ions bonded to oxygen: results for the transition metals and quantification of the factors underlying bond-length variation in inorganic solids.
IUCrJ
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Geological Sciences, University of Manitoba, 125 Dysart Road, Winnipeg, Manitoba R3T2N2, Canada.
Bond-length distributions are examined for 63 transition metal ions bonded to O in 147 configurations, for 7522 coordination polyhedra and 41 488 bond distances, providing baseline statistical knowledge of bond lengths for transition metals bonded to O. bond valences are calculated for 140 crystal structures containing 266 coordination polyhedra for 85 transition metal ion configurations with anomalous bond-length distributions. Two new indices, Δ and Δ, are proposed to quantify bond-length variation arising from bond-topological and crystallographic effects in extended solids.
View Article and Find Full Text PDFOrbital disproportionation and spin crossover as a pseudo Jahn-Teller effect.
J Chem Phys
September 2006
Institute for Theoretical Chemistry, Chemistry and Biochemistry Department, The University of Texas at Austin, Austin, TX 78712-0165, USA.
It is shown that in systems with electronic half-closed-shell configurations of degenerate orbitals, e(2) and t(3) (which have totally symmetric charge distribution), ground state distortions from high-symmetry geometries may occur due to a strong pseudo Jahn-Teller effect (PJTE) in the excited states, resulting also in a novel phenomenon of PJT-induced spin crossover. There is no JTE neither in the ground state term nor in the excited terms (including degenerate terms) of these configurations but a strong PJT mixing between two excited states [((1)E+(1)A) [cross-filled circle] e and ((2)T(1)+(2)T(2)) [cross-filled circle] e in the e(2) and t(3) cases, respectively] pushes down the lower term to cross the ground state of the undistorted system and to form the global minimum with a distorted geometry. The analysis of the electronic structure of this distorted configuration shows that it is accompanied by orbital disproportionation: instead of proportional population of all degenerate orbitals by one electron each (as in the ground state of the undistorted system that follows Hund's rule), two electrons with opposite spins occupy one orbital, resulting in transformations of the type (e(theta);e(epsilon))-->(e(theta)e(theta)) for e(2) and (t(x);t(y);t(z))-->(t(x);t(x);t(z)) for t(3) systems.
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