3D-Bulk systems Periodic in three dimensions ·Crystal structures Defects and impurities ·Elastic modulus Electronic/orbital properties ·Magnetic properties
Crystal structures Defects and impurities Elastic modulus Electronic/orbital properties Magnetic properties 3D – Bulk systems Periodic in three dimensions
Crystal structures Fe3si 1 1.00000000000000 ISIF calculate calculate relax change change 5.667 0.000 0.000 force stress tensor ions cell shape cell volume 0.000 5.667 0.000 0.000 0.000 5.667 0 yes no yes no no Si Fe o 10 1 yes trace only" yes no no Direct 2 yes yes yes no no 0.00 0.00 0.00 0.75 0.25 0.25 3 yes yes yes yes yes 0.25 0.75 0.25 4 yes yes yes yes no 0.25 0.25 0.75 ·a,b,c 0.50 0.500.50 5 yes yes no yes no 0.75 0.750.75 ·a,B,Y 6 yes yes no yes yes 0.25 0.250.25 0.50 0.000.00 yes yes no no yes 0.00 0.500.00 ·Atomic coordination 0.50 0.500.00 (,y,z) 0.75 0.75 0.25 Large freedom in ISIF 3 may cause a 0.00 0.000.50 0.50 0.00 0.50 long-time optimization!>ISIF 6,2.... 0.75 0.25 0.75 0.00 0.500.50 Structural optimization is very important for 0.25 0.75 0.75 the following studies ofphysical properties
Crystal structures a, b, c α, β, γ Atomic coordination (x, y, z) Fe3Si 1.00000000000000 5.667 0.000 0.000 0.000 5.667 0.000 0.000 0.000 5.667 Si Fe 6 10 Direct 0.00 0.00 0.00 0.75 0.25 0.25 0.25 0.75 0.25 0.25 0.25 0.75 0.50 0.50 0.50 0.75 0.75 0.75 0.25 0.25 0.25 0.50 0.00 0.00 0.00 0.50 0.00 0.50 0.50 0.00 0.75 0.75 0.25 0.00 0.00 0.50 0.50 0.00 0.50 0.75 0.25 0.75 0.00 0.50 0.50 0.25 0.75 0.75 Large freedom in ISIF = 3 may cause a long-time optimization! → ISIF = 6, 2…. Structural optimization is very important for the following studies of physical properties
Crystal structures The sensible approach would be to calculate the total energy of our material as a function of the lattice constant. -3.60 2.0 DFT energy -3.62 Quadratic fit -3.64 Quadratic extrapolation -2.4- BM equation of state 金 -3.66 -3.68 -2.8 ◆ -3.70 ◆ -3.72 ■-c/a=1.60 -0-…c/a=1.633 -3.2 -3.74 -▲-c/a=1.66 -0-…c/a=1.70 2.12.22.32.42.52.62.72.82.93.0 -3.76+ -●-c/a=1.74 a(A) 2.352.40 2.452.502.552.602.652.702.752.80 a(A) Etou(a)Eou(ao)+a(a-ao)+B(a-ao)2 E(a,c)contour =dEror/dalao and B=dEtr/da2lo
Crystal structures The sensible approach would be to calculate the total energy of our material as a function of the lattice constant. E(a,c) contour
Crystal structures VASP Phonopy supercell>phonon dispersion https://atztogo.github.io/phonopy/ In physics,a phonon is a collective excitation in a 16 periodic,elastic arrangement of atoms or molecules in 14 condensed matter.It represents an excited state in the 12 quantum mechanical quantization of the modes of 10 vibrations of elastic structures of interacting particles. The phonon dispersion curves are calculated along 6 several lines of high symmetry,and only the phonon frequency density of states are required rather the dispersion curves. WKrL UW L K
Crystal structures VASP + Phonopy + supercell → phonon dispersion The phonon dispersion curves are calculated along several lines of high symmetry, and only the phonon frequency density of states are required rather the dispersion curves. In physics, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter. It represents an excited state in the quantum mechanical quantization of the modes of vibrations of elastic structures of interacting particles. https://atztogo.github.io/phonopy/
Defects and impurities The arrangement of atoms or molecules in most crystalline materials is not perfect. ·Point defects Substitutional larger atom 0000 0 --vacancy (Schottky) 0 0 0 --interstitial Vacancy O 0 0 Frenkel --substitutional 000 ● 0 0 O --Frenkel pair(A nearby pair of a 00 0 vacancy and an interstitial) Interstitial --antisite(atoms of different type 0 0 exchange positions) 0 --defects in amorphous Substitutional smaller atom Line defects (edge/screw dislocation...) Planar defects(grain boundaries, antiphase,stacking faults...) HCP Bulk defects(pore,cracks,or inclusions) ABA
Defects and impurities Point defects -- vacancy (Schottky) -- interstitial -- substitutional -- Frenkel pair (A nearby pair of a vacancy and an interstitial) -- antisite (atoms of different type exchange positions) -- defects in amorphous Line defects (edge/screw dislocation…) Planar defects (grain boundaries, antiphase, stacking faults…) Bulk defects (pore, cracks, or inclusions) The arrangement of atoms or molecules in most crystalline materials is not perfect