Electronic, elastic and piezoelectric properties of two-dimensional （2D） group-IV buckled monolayers （GeSi, SnSi and SnGe） are studied by first principle calculations. According to our calculations, SnSi and SnGe ...Electronic, elastic and piezoelectric properties of two-dimensional （2D） group-IV buckled monolayers （GeSi, SnSi and SnGe） are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d11d11 of SnSi and SnGe are 5.04pm/V and 5.42pm/V, respectively, which are much larger than 2D MoS2 （3.6pm/V） and are comparable with some frequently used bulk materials （e.g., wurtzite AlN 5.1pm/V）. Charge transfer is calculated by the L wdin analysis and we find that the piezoelectric coefficients （d11d11 and d31） are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.展开更多
Machine learning methods, one type of methods used in artificial intelligence, are now widely used to analyze two-dimensional (2D) images in various fields. In these analyses, estimating the boundary between two regio...Machine learning methods, one type of methods used in artificial intelligence, are now widely used to analyze two-dimensional (2D) images in various fields. In these analyses, estimating the boundary between two regions is basic but important. If the model contains stochastic factors such as random observation errors, determining the boundary is not easy. When the probability distributions are mis-specified, ordinal methods such as probit and logit maximum likelihood estimators (MLE) have large biases. The grouping estimator is a semiparametric estimator based on the grouping of data that does not require specific probability distributions. For 2D images, the grouping is simple. Monte Carlo experiments show that the grouping estimator clearly improves the probit MLE in many cases. The grouping estimator essentially makes the resolution density lower, and the present findings imply that methods using low-resolution image analyses might not be the proper ones in high-density image analyses. It is necessary to combine and compare the results of high- and low-resolution image analyses. The grouping estimator may provide theoretical justifications for such analysis.展开更多
Successful synthesis of single iron-phthalocyanie （FePc） framework layer on substrate and its transferrable properties open the door for decorating the separately distributed transition metals for exploring the dive...Successful synthesis of single iron-phthalocyanie （FePc） framework layer on substrate and its transferrable properties open the door for decorating the separately distributed transition metals for exploring the diverse properties. We have studied the effects of chemical modification on two-dimensional FePc organometallic framework with density functional theory. For simplicity, the non-metal atoms with variant valence electrons are used as prototypes to estimate the effects ＆ore chemical modifications with different functional groups. The thermo-stabilities of the non-metal atom decorated complex sheet materials have been estimated by the first-principles constant energy molecular dynamic simulations. Upon the non- metal atom adsorption, the magnetic moment could be changed from 2 ~tB to 0, 1, 2, and 3 ~tB per unit cell for the case of tetra-, penta-, hexa-, and hepta-valent non-metal modifications, respectively, showing interesting promise to tailor its magnetic properties for potential applications.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 51672208the National Science and Technology Pillar Program during the Twelfth Five-Year Plan Period under Grant No 2012BAD47B02+2 种基金the Sci-Tech Research and Development Program of Shaanxi Province under Grant Nos 2010K01-120,2011JM6010 and 2015JM5183the Shaanxi Provincial Department of Education under Grant No 2013JK0927the SRF for ROCS of SEM
文摘Electronic, elastic and piezoelectric properties of two-dimensional （2D） group-IV buckled monolayers （GeSi, SnSi and SnGe） are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d11d11 of SnSi and SnGe are 5.04pm/V and 5.42pm/V, respectively, which are much larger than 2D MoS2 （3.6pm/V） and are comparable with some frequently used bulk materials （e.g., wurtzite AlN 5.1pm/V）. Charge transfer is calculated by the L wdin analysis and we find that the piezoelectric coefficients （d11d11 and d31） are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.
文摘Machine learning methods, one type of methods used in artificial intelligence, are now widely used to analyze two-dimensional (2D) images in various fields. In these analyses, estimating the boundary between two regions is basic but important. If the model contains stochastic factors such as random observation errors, determining the boundary is not easy. When the probability distributions are mis-specified, ordinal methods such as probit and logit maximum likelihood estimators (MLE) have large biases. The grouping estimator is a semiparametric estimator based on the grouping of data that does not require specific probability distributions. For 2D images, the grouping is simple. Monte Carlo experiments show that the grouping estimator clearly improves the probit MLE in many cases. The grouping estimator essentially makes the resolution density lower, and the present findings imply that methods using low-resolution image analyses might not be the proper ones in high-density image analyses. It is necessary to combine and compare the results of high- and low-resolution image analyses. The grouping estimator may provide theoretical justifications for such analysis.
基金Project supported by the Research Fund of Taishan Scholar,China(Grant No.TSHW20101004)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2010AM027)the National Natural Science Foundation of China(Grant No.11074100)
文摘Successful synthesis of single iron-phthalocyanie （FePc） framework layer on substrate and its transferrable properties open the door for decorating the separately distributed transition metals for exploring the diverse properties. We have studied the effects of chemical modification on two-dimensional FePc organometallic framework with density functional theory. For simplicity, the non-metal atoms with variant valence electrons are used as prototypes to estimate the effects ＆ore chemical modifications with different functional groups. The thermo-stabilities of the non-metal atom decorated complex sheet materials have been estimated by the first-principles constant energy molecular dynamic simulations. Upon the non- metal atom adsorption, the magnetic moment could be changed from 2 ~tB to 0, 1, 2, and 3 ~tB per unit cell for the case of tetra-, penta-, hexa-, and hepta-valent non-metal modifications, respectively, showing interesting promise to tailor its magnetic properties for potential applications.
