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This work presents a systematic investigation of the spectroscopic properties at anharmonic force fields of ground electronic state ( X ˜ 1 A 1 ) of LiNH2, which are calculated using second-order Møller-Plesset perturbation theory (MP2) and density functional theory (DFT) with hybrid GGA and meta-hybrid GGA (M06-2X) exchange-correlation functional. Two high angular momentum basis sets of 6-311+g (2d, p) and 6-311++g (3df, 2pd) are used. The equilibrium geometries, ground-state rotational constants, harmonic frequencies, and quartic and sextic centrifugal distortion constants of LiNH2 are calculated and compared with corresponding experimental or theoretical data. The predicted accuracy of the calculated constants has been confirmed by analyzing the deviations with respect to experiment. In addition, the anharmonic constants, vibration-rotation interaction constants, force constants, and Coriolis coupling constants of LiNH2 are firstly obtained. The infrared spectrum is predicted and together with the first prediction on the higher-order anharmonic constants contributes to a better understanding of the vibrational and rotational characteristics of LiNH2, thus revealing its internal structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • The migration pathways and oxidation process of single V atom in UHV and oxygen condition are determined. • O 2 atmosphere would affect the stability and dynamic behavior of V atom and V 2 dimer greatly. • Surface and subsurface V atoms can be easily oxidized to VO x monomers under the condition of oxygen gas. • V 2 dimer is stable in UHV while can be easily decomposed and oxidized into VO x monomers under oxygen condition. The migration and oxidation of single V atom and V 2 dimer on the anatase TiO 2 (1 0 1) surface are systematically studied based on density functional theory (DFT) calculations. For a single V atom, migration on the surface is almost impossible at room temperature while diffusion between surface and subsurface is easy in ultra-high vacuum (UHV) conditon. Without O attraction, single V atom prefers to stay at subsurface interstitial sites. But in oxygen condition, the subsurface interstitial V atom will easily diffuse to the surface and be oxidized into VO n (n = 1–3) monomers. The V 2 dimer is dynamically stable on the TiO 2 (1 0 1) surface and favors to be embedded in the surface layer in UHV condition. However, it can be easily decomposed and oxidized into VO n monomers in the condition of O 2. Our results offer an deep insight for the formation mechanism of sublayer vadanium oxides on TiO 2 support, and will be instructive for synthesizing desired VO x /TiO 2 catalysts. [ABSTRACT FROM AUTHOR]

The successful demonstration of monolayer films as promising thermoelectric materials highlights alternative strategies to nanostructuring for achieving high thermoelectric efficiency. Due to this reason, the electronic structure and thermoelectric properties of the monolayer Sb2Te3 are studied by using the density functional theory and the semiclassical Boltzmann transport equation. The dynamical stability of the monolayer Sb2Te3 can be guaranteed by the absence of imaginary frequencies in the phonon band structure. The monolayer Sb2Te3 can reduce the lattice thermal conductivity. The Seebeck coefficient S of the p-type monolayer Sb2Te3 is almost three times as high as those of the n-type monolayer Sb2Te3. The power factor for p-type doping is significantly larger than that for the n-type doping. Our calculated ZT values for the monolayer Sb2Te3 are far higher than those of nanomaterials Sb2Te3, bulk Sb2Te3, and the eutectic PbTe-Sb2Te3 composites, indicating that the thermoelectric performance of low-dimensional structure is indeed superior. [ABSTRACT FROM AUTHOR]

Nowadays, two-dimensional materials are ideal for fabricating optoelectronic and spintronic devices. We have investigated the optical and magnetic properties of −6 % to 6 % strain on Mn-adsorbed monolayer SnSe 2 films using a first-principles approach. The Mn-adsorbed monolayer SnSe 2 is a magnetic semiconductor in the absence of strain effects. As the tensile strain increases, the band gap of the Mn-adsorbed monolayer SnSe 2 decreases and the structure becomes unstable, and Mn adsorption changes to exothermic adsorption at −6 % strain. The magnetic moment of the system increases slightly with increasing tensile strain and decreases rapidly when the strain reaches 4%. As the compressive strain increases, the magnetic moment first decreases slightly and then decreases rapidly when the strain reaches −4 %. Calculations of the optical properties show that the static dielectric constants at −6 %, −4 %, −2 %, 0 %, 2 %, 4 % and 6 % strains are 15.23, 10.19, 8.67, 7.78, 6.38, 5.99 and 5.92, respectively, which increase with increasing compressive strain. It decreases with increase in tensile strain. The static dielectric function increases as the compressive strain increases and decreases as the tensile strain increases. In the visible light region, the reflectivity, refractive index, extinction coefficient and photoconductivity in the XX and ZZ directions increase with increasing tensile strain. Our study shows that the optoelectronic and magnetic properties of the SnSe 2 adsorbed Mn system can be improved to some extent by applying strain, and this study is expected to provide theoretical guidance for the fabrication of SnSe 2 -based magnetic optoelectronic devices. [ABSTRACT FROM AUTHOR]

The equilibrium geometries of c-H 2 C 3 O at B3LYP/aug-cc-pVTZ and HCCCHO and CH 2 CCO at MP2 /aug-cc-pVTZ theoretical level. The three C atoms of c-H 2 C 3 O form a ring, and the three C atoms of the other two isomers form a chain. The difference of structure of three isomers result in the significant difference of spectral properties. [Display omitted] • The relationship between structure and spectral properties of isomers are analyzed. • The ingredients of complex vibration modes of three isomers of C 3 H 2 O are discussed. • The geometries, energies and a series of spectral constants of isomers are predicted. The spectroscopic parameters and anharmonic force fields of three isomers (c-H 2 C 3 O, HCCCHO and CH 2 CCO) of C 3 H 2 O have been calculated by Density Functional Theory (B3LYP, CAM-B3LYP, wB97XD) and second-order Møller-Plesset perturbation theory (MP2) combining with 6–311++G (3df, 3pd) and aug-cc-pVTZ basis sets. The equilibrium geometries, energies, rotational constants, harmonic and fundamental frequencies, and centrifugal distortion constants of three isomers of C 3 H 2 O are calculated and compared with the existed results. The anharmonic constants, vibration–rotation interaction constants, Coriolis coupling constants and force constants of three isomers of C 3 H 2 O are firstly predicted. The ingredients of complex vibration modes, and infrared spectral characteristics of three isomers as well as the relationship between structure and spectroscopic properties are detailedly discussed. [ABSTRACT FROM AUTHOR]

The exploration for the four possible isomers of sulfur trioxide (SO 3) has led to the analysis of spectroscopic constants and anharmonic force fields for cis-OSOO, trans-OSOO, OS(=O) O and SOOO. Quantum chemical calculations are performed with Density Functional Theory (DFT) by employing B3LYP, B3P86 and B3PW91 three different functionals, in combination with Dunning's correlation-consistent cc-pVnZ, aug-cc-pVnZ (n = T, Q) basis sets. The equilibrium geometries, energies, force constants, a series of spectroscopic constants of these four isomers of SO 3 are calculated. The relationship between their structures and spectroscopic properties are analyzed in detail. The present results well reproduce the previous corresponding theoretical or experimental values. Therefore, we hope that our predictions on the isomers of SO 3 can provide the useful reference to further study their spectroscopic properties. Unlabelled Image • All four isomers of SO 3 have stable structures and their energies closely related to their structures. • The equilibrium geometries, energies and a series of spectroscopic constants for four isomers of SO 3 are predicted. • The relationship between the structures of four isomers of SO 3 and spectroscopic properties are analyzed in detail. [ABSTRACT FROM AUTHOR]

Layered materials are generally considered to be good candidates for thermoelectric materials, and the monolayer ZrNCl and HfNCl obtained from layered material ZrNCl and HfNCl should have lower lattice thermal conductivity. Here the electronic structure and thermoelectric properties of monolayer ZrNCl and HfNCl are studied by the first principles and the semi-classical Boltzmann theory. It is found that the DOS of HfNCl is larger than that of ZrNCl near Fermi surface, which shows that Seebeck coefficient of HfNCl are also larger than that of ZrNCl. The high frequency of the acoustic branch of HfNCl is relatively low, therefore, the lattice thermal conductivity of HfNCl is lower. The electrical conductivity of HfNCl is larger than that of ZrNCl. Therefore, HfNCl have good thermoelectric transport performance and high thermoelectric optimal value. ZT as a function of temperature for monolayer ZrNCl (Left) and monolayer HfNCl (Right). The Seebeck coefficient and electrical conductivity of HfNCl is larger than that of ZrNCl, nevertheless the lattice thermal conductivity of HfNCl is smaller than that of ZrNCl. Therefore, HfNCl have good thermoelectric transport performance and high thermoelectric optimal value. Image 1 • Seebeck coefficient of HfNCl are also larger than that of ZrNCl. • High frequency of acoustic branch of HfNCl causes lower lattice thermal conductivity. • The electrical conductivity of HfNCl is larger than that of ZrNCl. • HfNCl have good thermoelectric transport performance. [ABSTRACT FROM AUTHOR]

Influence of isotope effect on vibration frequency and rotation constant of H 2 PO at CAM-B3LYP/QZ level. • Spectroscopic constants and anharmonic force fields of H 2 PO and D 2 PO free radicals are predicted. • CAM-B3LYP/cc-pVQZ level theoretical levels are reasonable to H 2 PO and D 2 PO free radicals. • Influence of isotope effect on spectroscopic constants and anharmonic force fields of H 2 PO are studied. This work presents a systematic theoretical study on the calculation of the spectroscopic constants of H 2 PO and D 2 PO free radicals, computed with Density Functional Theory (DFT). Different functionals of B3LYP, CAM-B3LYP, CAM-B3LYP-D3(BJ), B3LYP-D3(BJ), and wB97XD are employed and discussed in details. Our results of CAM-B3LYP/ cc-pVQZ are in nice agreement with the experiment. The remarkable isotope effect is addressed and discussed. The nice results demonstrate that our predicted values of anharmonic constants and vibrational frequencies, centrifugal distortion constants, vibration-rotation interaction constants, and unknown anharmonic force field of H 2 PO and D 2 PO free radicals are accurate enough to provide a theoretical support. [ABSTRACT FROM AUTHOR]

The edge of phonon spectrum, that is, the highest optical frequency is only 170 cm−1, which will cause the large optical mode scattering. The strong coupling of acoustic and optical modes will enhance phonon scattering. Phonon optical modes contribute little to thermal conductivity. The lattice thermal conductivity of monolayer Sb 2 Te 2 Se is very low, only 0.46 W/mK at 300 K, it's less than 0.85W/mK of TlBiSe 2. The lattice thermal conductivity of monolayer Sb 2 Te 2 Se is less than 0.06 W/mK at 1000 K. The lattice thermal conductivity of monolayer Sb 2 Te 2 Se is much lower. The reasons for the low thermal conductivity of monolayer Sb 2 Te 2 Se are as follows. First of all, monolayer Bi 2 Te 2 Se contains heavy elements. Secondly, the small band gap between acoustic and optical branches causes the large phonon scattering rate is and the small average free path is, which will produce small K l. • The seebeck coefficient is the highest at 300 K. • The lattice thermal conductivity is much lower than other thermoelectric materials. • The heavy elements and small band gap cause the low thermal conductivity. • The strong coupling of acoustic and optical modes causes lower lattice thermal conductivity. • For the better n-type, Z e T reaches 1.5 at a temperature of 1000 K. The electronic structure and thermoelectric properties of monolayer Sb 2 Te 2 Se are studied by density functional theory and semi-classical Boltzmann transport equation. The Seebeck coefficient for monolayer Sb 2 Te 2 Se is very high, comparing with other thermoelectric materials. The strong coupling of acoustic and optical modes enhanced phonon scattering, which will cause lower lattice thermal conductivity. The heavy elements and small band gap cause the low thermal conductivity of monolayer Sb 2 Te 2 Se, so the lattice thermal conductivity of monolayer Sb 2 Te 2 Se is much lower than other thermoelectric materials. The optimal value Z e T of monolayer Sb 2 Te 2 Se is so high, mainly due to the very low lattice thermal conductivity. For the better n-type, Z e T reaches 1.5 at a temperature of 1000 K, which proves that monolayer Sb 2 Te 2 Se is a good choice for thermoelectric materials. [ABSTRACT FROM AUTHOR]

The electronic structure and thermoelectric properties of monolayer Bi 2 Te 2 Se were studied by density functional theory and semi-classical Boltzmann transport equation. The band gap with TB-mBJ can be improved for monolayer Bi 2 Te 2 Se. Monolayer Bi 2 Te 2 Se have ultra-low thermal conductivity comparing with other well-known two-dimensional materials. The monolayer Bi 2 Te 2 Se can improve electrical conductivities. ZT increases with increasing temperature for monolayer Bi 2 Te 2 Se. Comparing to GGA, TB-mBJ has larger ZT value in p-type doping. Monolayer Bi 2 Te 2 Se have larger ZT comparing with other well-known two-dimensional materials. Our calculated results show that our calculation greatly underestimates ZT value, therefore, monolayer Bi 2 Te 2 Se should have a higher ZT value. • Monolayer Bi 2 Te 2 Se have ultra-low thermal conductivity. • The monolayer Bi 2 Te 2 Se can improve electrical conductivities. • TB-mBJ can't reduce the electronic thermal conductivity. • Comparing to GGA, TB-mBJ has larger ZT value in p-type doping. • Monolayer Bi 2 Te 2 Se have larger ZT comparing with other well-known two-dimensional materials. [ABSTRACT FROM AUTHOR]