Direct energy bandgap materials are crucial for the efficient optoelectronics devices. Therefore, the investigation of new direct gap materials is important. In the present work, two novel d-metal sulfides Sc2CdS4 and Y2CdS4 compounds are investigated by using the all electron full potential linearized augment plane wave method. Both the compounds show semiconducting nature and direct band gap with a value 1.886eV for Sc2CdS4 and 2.209eV for Y2CdS4, respectively. Strong hybridization between S-p and Sc/Y-d orbitals present among valence and conduction bands which is beneicial to electrical transport. Key optical parameters are calculated. The static value of the reflectivity R(0) and refractive index n(0) are vary inversely with the energy band gap (Eg). Both the compounds Sc2CdS4 and Y2CdS4 are P-type thermoelectric materials because the Hole carriers dominate the electronic transport. High optical and thermal response for all compounds reveals that they are potential candidates for optical and thermoelectric devices.
Prediction of topological insulating behavior in Hg2CuTi-type Heusler compounds from first principles
采用密度泛函理论中的第一性原理计算，研究了具有Hg 2CuTi结构的X2 YZ Heusler化合物的拓扑能带结构.我们的研究结果清楚地表明，大量的Hg_2CuTi型Heusler化合物自然地表现出明显的带反转特征，这主要是由Y-Z锌双晶亚晶格控制的。Hg 2CuTi型Heusler化合物与半Heusler族化合物相似，其拓扑能带阶对晶格常数的变化非常敏感，且大多数化合物具有负的形成能，这使得它们更适合于材料生长，并且通过合金化或适当的应变可以容易地实现拓扑绝缘行为。
First-principles calculations were performed, and the results from the study of structural, electronic and elastic properties of zincblende III-arsenide binary compounds (BAs, AlAs, GaAs and InAs) are presented. These properties have been calculated using an ab initio pseudopotential method based on density functional theory (DFT) with the local density approximation (LDA) for the exchange-correlation potential. The results obtained for the calculated properties have been compared with experimental data and other computational works. It has also been found that our results with LDA are in good…
We investigate the effects of various dopants (M = K--Br) on the Curie temperature of the magnetic compound NdFe12 through first-principles calculations. Analysis by the Korringa--Kohn--Rostoker method with the coherent potential approximation reveals that doping the Fe sites with optimal concentrations of Ge and As is a promising strategy for increasing the Curie temperature. To search over a wider space, we also perform Bayesian optimization. Out of over 180,000 candidate compositions, co-doped systems with Co, Ge, and As are found to have the highest Curie temperatures.
Lattice defects affect the long-term stability of halide perovskite solar cells. Whereas simple point defects, i.e., atomic interstitials and vacancies, have been studied in great detail, here we focus on compound defects that are more likely to form under crystal growth conditions, such as compound vacancies or interstitials, and antisites. We identify the most prominent defects in the archetype inorganic perovskite CsPbI$_3$, through first-principles density functional theory (DFT) calculations. We find that under equilibrium conditions at room temperature, the antisite of Pb substituting Cs…
Physical properties of Thallium-Tellurium based thermoelectric compounds using first-principles simulations
采用密度泛函理论计算方法，研究了Tl_5Te_3，BiTl_9Te_6和SbTl_9Te_6化合物的热力学和物理性质.优化得到的化合物晶格常数与实验值符合较好。计算了三种化合物的电子态密度和能带结构，以了解它们的成键机制。BiTl 9 Te 6和SbTl 9 Te 6化合物的间接带隙分别为0.256eV和0.374eV。自旋-轨道耦合对两种半导体化合物的电子结构有重要影响，因此应该包括这些材料的良好的数值描述。计算了这三种化合物的弹性常数，测定了它们的体积模量、剪切模量和杨氏模量。Sb、Bi合金化后的韧脆转变与电子性质的变化有关。最后，得到了德拜温度、纵向声速、横向声速和平均声速。
Study of the structural and electronic properties of semimetallic InBi: first-principles calculation of compound with peculiarities of the electronic structure
First-principles prediction of redox potentials in transition-metal compounds with LDA+U
局域密度近似（LDA）或广义梯度近似（GGA）中的第一性原理计算虽然非常成功，但已知低估了氧化还原电位，例如锂嵌入过渡金属化合物的氧化还原电位。我们认为，这种不准确性与LDA/GGA中电子自相互作用误差的抵消不足有关，并且可以通过使用DFT+ $U$方法对$U$参数进行自洽评估来改善。我们表明，使用这种方法，实验嵌锂电压的过渡金属化合物，包括橄榄石锂$_{x}$ MPO $_{4}$（M=Mn，Fe Co，Ni），层状锂$_{x}$ MO $_{2}$（$x=$ Co，Ni）和尖晶石样锂$_{x}$ M $_{2}$ O $_{4}$（M=Mn，Co），可以准确地再现。
Recent attempts at topological materials have revealed a large class of materials that show gapless surface states protected by time-reversal symmetry and crystal symmetries. Among them, topological insulating states protected by crystal symmetries, rather than time-reversal symmetry are classified as topological crystalline insulators. We computationally predict the signature of new three-dimensional topological crystalline insulating compounds of space group 139(I/4mmm). After conducting a full volume optimization process by allowing to rearrange of atomic positions and lattice parameters, t…
Topological nontrivial nature are the latest phases to be discovered in condensed matter physics with insulating bulk band gaps and topologically protected metallic surface states; they are one of the current hot topics because of their unique properties and potential applications. In this paper, we have highlighted a first-principles study of the structural stability and electronic behavior of the Na${}_{2}$AgX (X= As, Sb and Bi) full Heusler compounds, using the Full-Potential Linear Muffin-Tin Orbital (FP-LMTO) method. We have originated that the Hg${}_{2}$CuTi structure is appropriate in a…
Pressure-induced insulator-to-metal transition (IMT) has been studied in the van der Waals compound iron thiophosphate (FePS3) using first-principles calculations within the periodic linear combination of atomic orbitals method with hybrid Hartree-Fock-DFT B3LYP functional. Our calculations reproduce correctly the IMT at ~15 GPa, which is accompanied by a reduction of the unit cell volume and of the vdW gap. We found from the detailed analysis of the projected density of states that the 3p states of phosphorus atoms contribute significantly at the bottom of the conduction band. As a result, th…
Magnetovolume Effects in Heusler Compounds via First-Principles Calculations
Heusler合金由于具有高的磁热效应和磁体积效应，在包括磁制冷在内的多种应用中具有广阔的前景。优化这种潜力的一种方法是通过增加磁体积效应。采用密度泛函理论和Korringa-Kohn-Rostoker方法，计算了几种L2 1型Co2 YZ Heusler合金的有效交换相互作用能和相应的平均场居里温度随体积（静水压力）的变化.不同的定性趋势和迹象的居里温度和力矩的压力导数中发现这些化合物，讨论和以前的计算和实验进行比较。
The spin-orbit -induced spin splitting of energy bands in low symmetry compounds (the Rashba Effect) has a long-standing relevance to spintronic applications and to the fundamental understanding of symmetry breaking in solids, yet the knowledge of what controls its magnitude in different materials is difficult to anticipate. Indeed, rare discoveries of compounds with large Rashba coefficients are invariably greeted as pleasant surprises. We advance the understanding of the "Rashba Scale" using the "inverse design" approach by formulating theoretically the relevant design principle and then ide…
The structural stability of CeFe$_{12}$ is investigated by using first-principles calculation. The formation energies of CeFe$_{12}$ relative to the Ce$_{2}$Fe$_{17}$ + bcc-Fe phase and to the CeFe$_{2}$ + bcc-Fe phase are calculated with the assumptions of trivalency and tetravalency for Ce. Those values are compared with corresponding results in $R$Fe$_{12}$ for $R=$ Nd, Sm, and Zr. Our results suggest that the tetravalent Ce is a promising stabilizer of the ThMn$_{12}$ structure. We also show that the stabilizing effect of an element depends as much on the valency as on the size of the $R$ …
Ni-Mn based ternary Heusler compounds have drawn attentions lately as significant magneto-caloric effects in some of them have been observed. Substitution of Ni and Mn by other $3d$ transition metals in controlled quantity have turned out to be successful in enhancing the effect and bring the operational temperatures closer to the room temperature. Using density functional theory calculations, in this work, we have systematically explored the roles of various factors such as site occupancies, magnetic interactions, and compositions associated with the constituents of Mn-excess Ni$_{2}$MnSb Heu…
The magnetic and optical properties of titanium dichalcogenide compounds, TiX$_2$ (X = S, Se and Te) have been calculated by first principles calculations using density functional theory (DFT) as implemented in SIESTA code. A 3x3 supercell of the compounds is taken in this study to be able to tune the properties obtained from the unit cell of these compounds. With magnetic states (ferromagnetic nature) as the attained ground state, spin polarized calculations are performed to obtain the mentioned properties. Further, with spin polarization into effect, external electric field (along z-directio…
First principle investigations of the structural, electronic and magnetic properties of the new zirconium based full-Heusler compounds, Zr2MnZ (Z = Al, Ga and In)
New Ternary Superconducting Compound LaRu2As2: Physical Properties from DFT Calculations
在本文中，我们提出了密度泛函理论（DFT）的第一性原理赝势方法内进行的计算，研究新发现的超导体LaRu 2 As 2的物理性质的第一次。优化后的结构参数与实验结果吻合较好。计算的独立弹性常数确保了化合物的机械稳定性。计算的Cauchy压力、Pugh比和泊松比表明LaRu_2As_2是一种韧性材料。由于低德拜温度，LaRu2As2可以用作热障涂层（TBC）材料。新化合物应表现出金属性质，因为其价带与导带相当大地重叠。LaRu2As2由于其6.8Gpa的低硬度值，预计是一种软材料并且易于加工。在计算的费米面中观察到了多带性质。根据电荷密度计算，预期离子、共价和金属相互作用的高度各向异性组合。
First-principles study on the intermediate compounds of LiBH$_4$
本文报道了LiBH $_4$中间体的第一性原理计算结果。用基于密度泛函理论的超软赝势方法研究了LiB $_3$ H $_8$和LiPDMATHABMP B $_n$ H $_n (n=5-12)$的稳定性.理论预测表明，单斜晶系Li $_2$ B $_{12}$ H $_{12}$是最稳定的候选材料.我们提出了以下通过该中间体化合物进行LiBH $_4$的氢化/脱氢过程：LiBH $_4 \leftrightarrow {1/12}$ Li $_{2}$ B $_{12}$ H $_{12} + {5/6}$ LiH $+ {13/12}$ H $_2 \leftrightarrow $ LiH $+$ B $+ {3/2} $ H $_2$。第一反应的氢含量和焓估计分别为10质量%和56 kJ/mol H $_2$，第二反应的氢含量和焓估计分别为4质量%和125 kJ/mol H $_2$。它们与LiBH $_4$的热脱附谱的实验结果符合得很好。计算结果表明，单斜LiPDMATHABMP B $_{12}$ H $_{12}$的$Γ$ -声子频率的弯曲模比LiBH $_4$的低，而伸缩模则高.这些结果对于实验研究和鉴定可能的中间体化合物是非常有用的。
The fundamental properties of infinite-layer rare-earth nickelates (RNiO2) are carefully revisited and compared with those of CaCuO2 and RNiO3 perovskites. Combining first-principles and finite-temperature second-principles calculations, we highlight that bulk NdNiO2 compound are far from equivalent to CaCuO2, together at the structural, electronic, and magnetic levels. Structurally, it is shown to be prone to spin-phonon coupling induced oxygen square rotation motion, which might be responsible for the intriguing upturn of the resistivity. At the electronic and magnetic levels, we point out o…
First-principles high-throughput screening of ruthenium compounds for advanced interconnects
Department of Electronics Engineering, Incheon National University（仁川国立大学电子工程系）；Research Institute for Engineering and Technology, Incheon National University（仁川国立大学工程技术研究院）
Investigation on different physical aspects such as structural, elastic, mechanical, optical properties and Debye temperature of Fe2ScM (M = P and As) semiconductors: a DFT based first principles study
As a possible alternative to organic-inorganic hybrid perovskite halide, inorganic Cs2SnI6 has drawn more and more research attention recently. In order to find more Cs2SnI6 derivatives as the potential solar cell absorber materials, I- ions in Cs2SnI6 are replaced by other halogen ions and forms the Cs2SnI6-nXn (X=F, Cl, Br; n=1~6) compounds, whose atomic structures, electronic structures and optical absorption are investigated by first principles calculation. When the alloying level n increases, the mean lattice constants, the weighted Sn-X and Cs-X bond lengths all decreases linearly; the b…
