scholarly journals PREDICTION OF FORMATION ENERGY USING TWO-STAGE MACHINE LEARNING BASED ON CLUSTERING

2021 ◽  
Vol 55 (2) ◽  
pp. 263-268
Author(s):  
Xingyue Fan
Keyword(s):  
Machine Learning ◽  
Density Functional ◽  
Formation Energy ◽  
Boosted Regression Trees ◽  
Random Forest Regression ◽  
Two Stage ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Gradient Boosted Regression Trees ◽  
Cluster 2

The formation energy (Hf) is one of the important properties associated with the thermodynamic stability of ABO3-type perovskite. In this work, two-stage machine learning based on hierarchical clustering and regression was designed for improving the prediction values of the density-functional theory (DFT) Hf of ABO3-type perovskites. A global dataset was clustered into Cluster 1 and Cluster 2 using the CHI (the Calinski-Harabasz index). To compare the prediction performances of Hf, DTR (decision tree regression), GBRT (gradient boosted regression trees), RFR (random forest regression) and ETR (extra tree regression) were applied to build models of Cluster 1, Cluster 2 and the global dataset, respectively. The results showed that all four different regression models of Cluster 1 had a higher R2, and lower MSE and MAE than those of the global dataset, while the models of Cluster 2 were poorer. Meanwhile, the GBRT model of Cluster 1 achieved a higher R2 of 0.917, and lower MSE and MAE of 0.033 eV/atom and 0.125 eV/atom. We further validated and compared the generalization ability of the models by predicting the Hf of ABO3-type perovskite previously unseen in the training set. The two-stage machine-learning models proposed here can provide useful guidance for accelerating the exploration of materials with desired properties.

Theoretical Study of the Electronic Structures of Li-Doped ZnO

2012 ◽  
Vol 535-537 ◽  
pp. 214-218
Author(s):  
Qi Xin Wan ◽  
Jia Yi Chen ◽  
Zhi Hua Xiong ◽  
Dong Mei Li ◽  
Bi Lin Shao ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Formation Energy ◽  
Lattice Distortion ◽  
Theoretical Study ◽  
Functional Theory ◽  
Li Doping ◽  
The Density Functional Theory ◽  
Doped Zno ◽  
Good Agreement

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the geometric structure, the formation energy of impurities and the electronic structure of Li-doped ZnO. In the system of Li-doped ZnO, LiZn can not result in lattice distortion. In contrast with that case, LiO and Lii result in lattice distortion after Li doping in ZnO. In Li-doped ZnO, LiO is the most unstable than the other cases. Simultaneously, Lii is more stable than LiZn according to that Lii has smaller formation energy. Furthermore, the electronic structure of Li-doped ZnO indicates that that LiZn behaves as acceptor, while Lii behaves as donor. In conclusion, in Li-doped ZnO, Lii is always in the system to compensate the acceptor. Singly doping Li in ZnO is difficult to gain p-ZnO for the self-compensation. The results are in good agreement with other calculated and experimental results.

Mechanical and Electrical Properties of TiN with Stacking Fault: A DFT Study

2015 ◽  
Vol 727-728 ◽  
pp. 331-334
Author(s):  
Guo Xun Wu ◽  
Zhen Qing Wang ◽  
Chen Liang Li ◽  
Chao Ying Wang ◽  
Yong Yang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electrical Properties ◽  
Density Functional ◽  
Formation Energy ◽  
Stacking Faults ◽  
Uniaxial Tensile ◽  
Functional Theory ◽  
Mechanical And Electrical Properties ◽  
The Density Functional Theory ◽  
Uniaxial Tensile Stress

Using the density-functional theory, the mechanical and electrical properties of TiN crystal with stacking faults have been evaluated. The formation energy of stacking faults are calculated. It is found that the stacking faults can increase the strength of TiN crystal but attribute little effect for the electrical properties. The uniaxial tensile stress can lower the Fermi surface of the TiN crystal, and the metallic characteristic is weakened with the stress increasing.

First Principle Study on Mn-Doped Ceria with Different Doping Concentration

2013 ◽  
Vol 712-715 ◽  
pp. 541-545
Author(s):  
Zhi Guo Yan ◽  
Tong Jun Zhu ◽  
Ai Guo Xuan ◽  
Yuan Xin Wu
Keyword(s):  
Density Functional ◽  
Formation Energy ◽  
Doping Concentration ◽  
Structural Model ◽  
First Principle ◽  
Functional Theory ◽  
Electron Density Of States ◽  
The Density Functional Theory ◽  
Electronic Storage ◽  
Mn Doped

First-principle software bundle based on the density functional theory (DFT) is used to investigate pure CeOB2B and Mn-doped CeOB2B with different doping concentration. The structural model of CeOB2B crystal is constructed and geometrically optimized, the electron density of states and band structure calculated. The results are as follows: the valence band top of CeOB2B is made up with O2p and Ce5d states, and the existence of 4f unoccupied molecular orbital of CeOB2B facilitates the electronic storage. The theoretical calculation models of Mn-doped CeOB2B with different concentration are constructed and calculated, including 2*1*1, 2*2*1 and 2*2*2 supercell models. After CeOB2B is doped, hybridization happens between 4s orbitals of Mn atoms and 2p orbital of O atoms, resulting in 4s orbitals of Mn atoms lose electrons.Moreover, Mn atom is electron donor and O atoms is the electron acceptor. As the doping concentration decreases, the formation energy also decreases.And a smaller formation energy leads to a more stable structure.

Oxygen Vacancies in Amorphous HfO2 and SiO2

2008 ◽  
Vol 1073 ◽  
Author(s):  
Chioko Kaneta ◽  
Takahiro Yamasaki
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Oxygen Vacancies ◽  
Gate Dielectrics ◽  
Propagation Mechanism ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Difference ◽  
Formation Energies

ABSTRACTFormation energies and electronic properties of oxygen vacancies in amorphous HfO2 gate dielectrics are investigated by employing the first-principles method based on the density functional theory. We have found that the formation energy of neutral oxygen vacancy in amorphous HfO2 distributes from 4.7 to 6.1 eV, most of which is lower than the value for cubic HfO2, 6.0 eV. We also investigated the stabilities of the Vo pairs in various charged state and compared with those in amorphous SiO2. We found that Vo++ is stabilized in the vicinity of Vo in SiO2. In HfO2, however, this does not happen. This suggests the difference of defect propagation mechanism in HfO2 and SiO2.

Theoretical Study of the Electronic Structures of Na-Doped ZnO

2014 ◽  
Vol 665 ◽  
pp. 124-127 ◽  
Author(s):  
Qi Xin Wan ◽  
Bi Lin Shao ◽  
Zhi Hua Xiong ◽  
Dong Mei Li ◽  
Guo Dong Liu
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Formation Energy ◽  
Theoretical Study ◽  
The Other ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Doped Zno

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the formation energy of impurities and the electronic structure of ZnO doped with Na. In Na-doped ZnO, NaOis the most unstable than the other cases. Simultaneously, NaZnis more stable than Naiaccording to that NaZnhave smaller formation energy. Furthermore, the electronic structure of Na-doped ZnO indicates that that NaZnbehaves as an acceptor, while Naibehaves as a donor.

First-Principles Calculation of Defect Formation and Positron Annihilation States in Bi2Te3

2017 ◽  
Vol 373 ◽  
pp. 41-45 ◽  
Author(s):  
Bin Zhao ◽  
Bo Zhou ◽  
Chong Yang Li ◽  
Ning Qi ◽  
Zhi Quan Chen
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Defect Formation ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Rich Condition ◽  
The Density Functional Theory ◽  
Positron Wave Function ◽  
Positron Lifetimes

Defect formation energy in Bi2Te3 thermoelectric material was calculated using a first principles approach based on the Density Functional Theory (DFT). For vacancy-type defect, the Te1 vacancy (VTe1) is the most stable defect with low formation energy in both Bi-rich and Te-rich conditions, which indicates that the Te1 vacancies have higher probability to be formed. For antisite defects, the formation energy of BiTe1 is much lower than that of BiTe2 in Bi-rich condition, while in Te-rich condition it is beneficial for TeBi with lower formation energy. Positron wave function distribution and positron lifetimes of different annihilation states in Bi2Te3 were also calculated using the atomic superposition (ATSUP) method. The positron bulk lifetime in Bi2Te3 is about 231 ps, and for the neutral vacancy-type defects without relaxation, the positron lifetimes of VBi, VTe1 and VTe2 are 275 ps, 295 ps and 269 ps, respectively.

scholarly journals Structural and Electronic Properties of GaN (0001)/α-Al2O3(0001) Interface

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
M. B. Pereira ◽  
E. M. Diniz ◽  
S. Guerini
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Formation Energy ◽  
Structural Models ◽  
Interface Region ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Strong Hybridization ◽  
Α Al2o3

Structural and electronic properties of the interface betweenα-Al2O3(0001) and GaN (0001) surfaces are investigated throughab initiocalculations within the density functional theory. Two different structural models have been investigated interface N(Ga)-terminated. The interface N-terminated GaN surface seems to exhibit the lowest formation energy. The studied interface models are metallic, with the levels at energy spatially confined in the interface region. Our calculations show strong hybridization between atoms in the interface region.

scholarly journals Strain Investigation on Spin-Dependent Transport Properties of γ-Graphyne Nanoribbon Between Gold Electrodes

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yun Li ◽  
Xiaobo Li ◽  
Shidong Zhang ◽  
Liemao Cao ◽  
Fangping Ouyang ◽  
...  
Keyword(s):  
Transport Properties ◽  
High Performance ◽  
Density Functional ◽  
Strain Engineering ◽  
Molecular Junctions ◽  
Spin Splitting ◽  
Functional Theory ◽  
Spin Dependent Transport ◽  
The Density Functional Theory ◽  
Dependent Transport

AbstractStrain engineering has become one of the effective methods to tune the electronic structures of materials, which can be introduced into the molecular junction to induce some unique physical effects. The various γ-graphyne nanoribbons (γ-GYNRs) embedded between gold (Au) electrodes with strain controlling have been designed, involving the calculation of the spin-dependent transport properties by employing the density functional theory. Our calculated results exhibit that the presence of strain has a great effect on transport properties of molecular junctions, which can obviously enhance the coupling between the γ-GYNR and Au electrodes. We find that the current flowing through the strained nanojunction is larger than that of the unstrained one. What is more, the length and strained shape of the γ-GYNR serves as the important factors which affect the transport properties of molecular junctions. Simultaneously, the phenomenon of spin-splitting occurs after introducing strain into nanojunction, implying that strain engineering may be a new means to regulate the electron spin. Our work can provide theoretical basis for designing of high performance graphyne-based devices in the future.

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