First principles study of the electronic and magnetic structures of the tetragonal and orthorhombic phases of Ca3Mn2O7

On the basis of density functional theory electronic band structure calculations using the augmented spherical wave method, the electronic and magnetic properties of the orthorhombic and tetragonal phases of Ca3Mn2O7 were investigated and the spin exchange interactions of the orthorhombic phase were analyzed. Our calculations show that the magnetic insulating states are more stable than the non-magnetic metallic state for both polymorphs of Ca3Mn2O7, the orthorhombic phase is more stable than the tetragonal phase, and the ground state of the orthorhombic phase is antiferromagnetic. The total energies calculated for the three spin states of the orthorhombic phase of Ca3Mn2O7 led to estimates of the spin exchange interactions Jnn = -3.36 meV and Jnnn = -0.06 meV. The accuracy of these estimates were tested by calculating the Curie-Weiss temperature within the mean-field approximation.Comment: 11 pages, 7 figure

First principles investigation of the electronic structure of La2MnNiO6: A room-temperature insulating ferromagnet

Using first principles calculations within DFT based on the full potential APW+lo method, we calculated the electronic and magnetic structures for the ferromagnetic and antiferromagnetic states of La2MnNiO6 and analyzed the site projected density of states and electronic band structures. Our calculations show that the ground state of La2MnNiO6 is ferromagnetic insulating with the magnetization in agreement with Hund's first rule and experimental findings.Comment: 10 pages, 3 figure

Thromboembolism and bleeding in systemic amyloidosis: a review

The assessment of both thromboembolic and haemorrhagic risks and their management in systemic amyloidosis have been poorly emphasized so far. This narrative review summarizes main evidence from literature with clinical perspective. The rate of thromboembolic events is as high as 5–10% amyloidosis patients, at least in patients with cardiac involvement, with deleterious impact on prognosis. The most known pro-thrombotic factors are heart failure, atrial fibrillation, and atrial myopathy. Atrial fibrillation could occur in 20% to 75% of systemic amyloidosis patients. Cardiac thrombi are frequently observed in patients, particularly in immunoglobulin light chains (AL) amyloidosis, up to 30%, and it is advised to look for them systematically before cardioversion. In AL amyloidosis, nephrotic syndrome and the use of immunomodulatory drugs also favour thrombosis. On the other hand, the bleeding risk increases because of frequent amyloid digestive involvement as well as factor X deficiency, renal failure, and increased risk of dysautonomia-related fall

Pressure dependence of elastic constants and related parameters for rocksalt MgO

Based on the full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in both the local density approximation (LDA) and the generalized gradient approximation (GGA) approaches, the elastic constants and some of their related parameters such as the bulk modulus, shear modulus, [1 0 0] Young's modulus, anisotropy factor, [1 0 0] Poisson's ratio, and internal strain parameter have been reported for MgO in the rocksalt structure. The overall agreement between our results and the available experimental and theoretical data is found to be reasonably good. The pressure dependence of all studied quantities has been investigated. The mechanical stability criteria for the material of interest for pressures up to 100 GPa are fulfilled

Lattice dynamical properties and interatomic force constants of natural and artificial ABO3/AO superlattices

Peer reviewe

New considerations on the role of covalency in ferroelectric niobates and tantalates

Values of Curie temperature, TC, and microwave relaxation frequency, fr, of ferroelectric niobates and tantalates are found to be closely related to the metal-oxygen network covalency. Correlations previously evidenced in perovskite-type relaxors (PSN, PST) are confirmed here for K(Ta$_{1-x}$Nbx)O3 (KTN) compositions. The investigated physical characteristics, TC and fr, are determined via dielectric measurements performed in a wide frequency range (102–109 Hz) and as a function of temperature (250–800 K). On a theoretical point of view, bond covalencies are evaluated through tight-binding band structure calculations. The complex role of covalency on the metal potential is precised. Two antagonist effects acting on both the short-range interatomic repulsions and the rigidity and stability of the oxygen-metal network are discussed. The validity of this approach is comforted through the example of the oxyfluoride K3Li1.5Ta5O14.5F0.5

Pressure dependence of elastic constants and related parameters for rocksalt MgO

Based on the full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in both the local density approximation (LDA) and the generalized gradient approximation (GGA) approaches, the elastic constants and some of their related parameters such as the bulk modulus, shear modulus, [1 0 0] Young's modulus, anisotropy factor, [1 0 0] Poisson's ratio, and internal strain parameter have been reported for MgO in the rocksalt structure. The overall agreement between our results and the available experimental and theoretical data is found to be reasonably good. The pressure dependence of all studied quantities has been investigated. The mechanical stability criteria for the material of interest for pressures up to 100 GPa are fulfilled