We report a linear-scaling random Green's function(rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projec...We report a linear-scaling random Green's function(rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H_(2)O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H_(2)O clusters at T = 0 K can reach an error of~ 1 me V per H_(2)O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.展开更多
This work reveals the giant influence of spatial distribution of disordered surface roughness on electron tunneling,which is of immediate relevance to the magneto tunnel device and imaging technologies.We calculate th...This work reveals the giant influence of spatial distribution of disordered surface roughness on electron tunneling,which is of immediate relevance to the magneto tunnel device and imaging technologies.We calculate the spin-dependent tunneling in Fe/vacuum/Fe junction with disordered surface roughness with the first-principles non-equilibrium dynamical cluster theory.It is found that,at high concentration of surface roughness,different spatial distributions,including the clustered,anti-clustered and completely random roughness characterized by Warren–Cowley parameters,present large deviations from each other in all spin channels.By changing from clustered to anti-clustered roughness,it is surprising that spin polarization of tunneling in parallel configuration(PC)can be drastically reversed from-0.52 to 0.93,while complete randomness almost eliminates the polarization.It is found that the anti-clustered roughness can dramatically quench the tunneling of minority spin in both PC and anti-PC by orders of magnitude,but significantly enhance the transmission of majority spin in PC(by as large as 40%)compared to the results of clustered roughness,presenting distinct influences of differently correlated surface roughness.The spatial correlation of disordered surface roughness can significantly modify the surface resonance of Fe minority spin.展开更多
基金financial support from the National Natural Science Foundation of China (Grant No. 12227901)the financial support from the National Natural Science Foundation of China (Grant Nos. 11974263 and 12174291)。
文摘We report a linear-scaling random Green's function(rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H_(2)O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H_(2)O clusters at T = 0 K can reach an error of~ 1 me V per H_(2)O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.
基金financial support from the National Natural Science Foundation of China(Grant No.11874265)Shanghaitech Startup+1 种基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303300 and 2018YFB0407601)the National Natural Science Foundation of China(Grant Nos.11734004 and 21421003)。
文摘This work reveals the giant influence of spatial distribution of disordered surface roughness on electron tunneling,which is of immediate relevance to the magneto tunnel device and imaging technologies.We calculate the spin-dependent tunneling in Fe/vacuum/Fe junction with disordered surface roughness with the first-principles non-equilibrium dynamical cluster theory.It is found that,at high concentration of surface roughness,different spatial distributions,including the clustered,anti-clustered and completely random roughness characterized by Warren–Cowley parameters,present large deviations from each other in all spin channels.By changing from clustered to anti-clustered roughness,it is surprising that spin polarization of tunneling in parallel configuration(PC)can be drastically reversed from-0.52 to 0.93,while complete randomness almost eliminates the polarization.It is found that the anti-clustered roughness can dramatically quench the tunneling of minority spin in both PC and anti-PC by orders of magnitude,but significantly enhance the transmission of majority spin in PC(by as large as 40%)compared to the results of clustered roughness,presenting distinct influences of differently correlated surface roughness.The spatial correlation of disordered surface roughness can significantly modify the surface resonance of Fe minority spin.
