The role of dynamical polarization of the ligand to metal charge transfer excitations in {\em ab initio} determination of effective exchange parameters

The role of the bridging ligand on the effective Heisenberg coupling parameters is analyzed in detail. This analysis strongly suggests that the ligand-to-metal charge transfer excitations are responsible for a large part of the final value of the magnetic coupling constant. This permits to suggest a new variant of the Difference Dedicated Configuration Interaction (DDCI) method, presently one of the most accurate and reliable for the evaluation of magnetic effective interactions. This new method treats the bridging ligand orbitals mediating the interaction at the same level than the magnetic orbitals and preserves the high quality of the DDCI results while being much less computationally demanding. The numerical accuracy of the new approach is illustrated on various systems with one or two magnetic electrons per magnetic center. The fact that accurate results can be obtained using a rather reduced configuration interaction space opens the possibility to study more complex systems with many magnetic centers and/or many electrons per center.Comment: 7 pages, 4 figure

Monitoring training loads in professional basketball players engaged in a periodized training programme

The aims of this study were to investigate the dynamics of external (eTL) and internal (iTL) training loads during seasonal periods and examine the effect of a periodized training programme on physical performance in professional basketball players. Repeated measures for 9 players (28±6 yr; 199±8 cm; 101±12 kg) were collected from 45 training sessions, over a 6-wk pre-season phase and a 5-wk in-season phase. Physical tests were conducted at baseline (T1), week 4 (T2) and week 9 (T3). Differences in means are presented as % ± Confident Limits (CL). A very likely difference was observed during in-season compared to pre-season for the eTL variables measured by GPS: mechanical load (13.5±8.8) and peak acceleration (11.0±11.2) respectively. Regarding iTL responses, a very large decrement in TRIMP (most likely difference, -20.6±3.8) and in session-RPE training load (very likely difference, -14.2±9.0) was detected from pre-season to in-season. Physical performance improved from T1 to T3 for: Yo-Yo Intermittent-Recovery Test 1, 62.2±34.3, ES>1.2; Countermovement Jump, 8.8±6.1, ES>0.6; and Squat Jump, 14.8±10.2, ES>0.8. Heart rate (HR; % HRpeak) exercise responses during a submaximal running test decreased from T1 to T3 (3.2±4.3, ES1.2). These results provide valuable information to coaches about training loads and physical performance across different seasonal periods. The data demonstrate that both eTL and iTL measures should be monitored in association with physical tests to provide a comprehensive understanding of the training process

Traveling length and minimal traveling time for flow through percolation networks with long-range spatial correlations

We study the distributions of traveling length l and minimal traveling time t through two-dimensional percolation porous media characterized by long-range spatial correlations. We model the dynamics of fluid displacement by the convective movement of tracer particles driven by a pressure difference between two fixed sites (''wells'') separated by Euclidean distance r. For strongly correlated pore networks at criticality, we find that the probability distribution functions P(l) and P(t) follow the same scaling Ansatz originally proposed for the uncorrelated case, but with quite different scaling exponents. We relate these changes in dynamical behavior to the main morphological difference between correlated and uncorrelated clusters, namely, the compactness of their backbones. Our simulations reveal that the dynamical scaling exponents for correlated geometries take values intermediate between the uncorrelated and homogeneous limiting cases

Exchange coupling in CaMnO3_3 and LaMnO3_3: configuration interaction and the coupling mechanism

The equilibrium structure and exchange constants of CaMnO$_3$ and LaMnO$_3$ have been investigated using total energy unrestricted Hartree-Fock (UHF) and localised orbital configuration interaction (CI) calculations on the bulk compounds and Mn$_2$O$_{11}^{14-}$ and Mn$_2$O$_{11}^{16-}$ clusters. The predicted structure and exchange constants for CaMnO$_3$ are in reasonable agreement with estimates based on its N\'eel temperature. A series of calculations on LaMnO$_3$ in the cubic perovskite structure shows that a Hamiltonian with independent orbital ordering and exchange terms accounts for the total energies of cubic LaMnO$_3$ with various spin and orbital orderings. Computed exchange constants depend on orbital ordering. UHF calculations tend to underestimate exchange constants in LaMnO$_3$, but have the correct sign when compared with values obtained by neutron scattering; exchange constants obtained from CI calculations are in good agreement with neutron scattering data provided the Madelung potential of the cluster is appropriate. Cluster CI calculations reveal a strong dependence of exchange constants on Mn d e$_g$ orbital populations in both compounds. CI wave functions are analysed in order to determine which exchange processes are important in exchange coupling in CaMnO$_3$ and LaMnO$_3$.Comment: 25 pages and 9 postscript figure

Proper ferroelectric transition in the multiferroic YMnO3

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