Sb Sites Research Articles

Effects of Sn-Doping on the Thermoelectric Properties of Famatinite

Various Sn-doped famatinite (Cu3Sb1−ySnyS4, 0 ≤ y ≤ 0.1) specimens were prepared by employing a mechanical alloying and hot-pressing method. The phase transitions, microstructures, and thermoelectric properties, i.e., the electrical conductivity, Seebeck coefficient, power factor, thermal conductivity, Lorenz number, and figure of merit, were examined. The famatinite phase with a tetragonal structure was stable below its melting point, as no secondary phases were present; however, it transformed to skinnerite Cu3SbS3 at higher temperatures. Sn doping reduced the melting point from 817 K (Cu3SbS4) to 815 K (Cu3Sb0.92Sn0.08S4). Hot-pressed compacts exhibited relative densities of 97.1–99.5%. Because Sn replaced at Sb sites, the a-axis slightly reduced, and the c-axis increased. Cu3SbS4 exhibited non-degenerate semiconductor behavior, and possessed a low dimensionless figure of merit (ZT) of 0.1 at 623 K; these phenomena were products of the power factor of 0.14 mW m−1 K−2 and thermal conductivity of 0.62 W m−1 K−1. Conversely, the Sn-doped specimens exhibited degenerate semiconductor characteristics. As the Sn content increased, the electrical and thermal conductivities and power factor increased, whereas the Seebeck coefficient decreased. The thermoelectric performance was significantly enhanced by Sn doping. The highest ZT (0.67 at 623 K) was obtained for Cu3Sb0.92Sn0.08S4, and it was a product of implementing a power factor of 0.94 mW m−1 K−2 and thermal conductivity of 0.86 W m−1 K−1.

Possible observation of Kondo screening cloud in Yb14MnSb11

ABSTRACTSingle crystals of the underscreened Kondo ferromagnet Yb14MnSb11 were investigated using polarised neutron diffraction and magnetisation measurements. The magnitude and direction of the magnetisation at each of the 9 distinct crystallographic sites was measured using polarised neutron diffraction. A large moment of close to 4.2 μB was found at the unique Mn site. A compensating antiferromagnetic moment of ≈−0.5 μB was found to be distributed uniformly among the remaining Yb and Sb sites, which was not expected from a previous theoretical calculation. The compensating magnetisation, however, is consistent both in size and magnitude with the expected Kondo screening cloud.

Enhancement in the thermoelectric properties of Cu3SbSe4 by Sn doping

The solid-state reaction technique was employed to fabricate Sn doped Cu3SbSe4 samples. The effect of doping on structural and thermoelectric properties of Cu3SbSe4 samples is represented in the present communication. The powder X-ray diffraction pattern of all the samples show that they have tetragonal structure (space group $$I\bar{4}2m$$ ). It is observed that doping Sn at Sb site acts as acceptor dopant which enhances hole concentration. The temperature dependent electrical resistivity (ρ(T)) is observed to decrease with increase in Sn concentration up to x = 0.03, thereafter ρ(T) increases with the increase in x concentration. To explore the conduction mechanism, we have employed small poloron hopping (SPH) model to the ρ(T) data and the results indicate that SPH is operative in the high temperature regime for all samples. The data of Seebeck coefficient (S(T)) confirms that holes are the majority charge carriers for pristine as well as doped samples. The analysis of S(T) data reveals that all the samples have a narrow band gap. The contribution from electron thermal conductivity is found to be less than 1%, thus the total conductivity is mainly because of phonon thermal conductivity. The highest value of dimensionless figure of merit (ZT = 0.127) was achieved at 374 K for the sample Cu3Sb0.99Sn0.01Se3 which is slightly higher than that of the pristine sample (ZT = 0.115). The highest value of compatibility factor (0.98 V−1) was observed for the sample Cu3Sb0.98Sn0.02Se3 at 374 K.

The impact of vacancies on the stability of cubic phases in Sb\u2013Te binary compounds

Data retention ability and number of cycles are key properties of phase change materials in applications. Combining in situ heating transmission electron microscopy with ab initial calculations, we investigated the phase transitions of binary Sb–Te compounds. The calculations indicated that the vacancies in Te sites destroyed the framework of the cubic phase, which agrees well with the absence of cubic phases observed during in situ heating experiments when the Sb concentration exceeded 50%. In contrast, the vacancies in Sb sites stabilized the cubic structure. Further analysis of the charge density maps revealed that the distribution of antibonding electrons may be the origin of the driving force for structural transitions. Furthermore, our results also showed that reducing the vacancies greatly increased the phase transition temperatures of both the amorphous-cubic and cubic-trigonal phases and therefore may improve the data retention ability and cyclability of phase change materials. This result also implies that doping Sb–Te compounds may provide an approach to discover novel phase change materials by reducing the amount of vacancies.

Improvement of thermoelectric properties of Cu3SbSe4 hierarchical with in-situ second phase synthesized by microwave-assisted solvothermal method

Pb doped Cu3Sb1-xPbxSe4 (x = 0, 0.01, 0.02, 0.04 and 0.06) compounds have been synthesized via microwave-assisted solvothermal method followed by SPS progress, and their thermoelectric properties from 300 K to 623 K has been explored. On one hand, Pb doping in the Sb site improved the electrical properties of Cu3SbSe4, on the other hand, the second phase PbSe formed at the high doping content (x ≥ 0.02) reduced the thermal conductivity by the phonon scattering. Altogether, the improvement of the electrical properties and decrease of the thermal conductivity results in a promising peak zT of ∼0.52 at 623 K of Cu3Sb0.96Pb0.04Se4 sample, which is about 80% higher than that of the un-doped Cu3SbSe4. The current work provides a method which can reduce the thermal conductivity by forming heterojunction and also improve the electrical properties by doping of one element.

Organic conductors with BiIII and SbIII chloride-based anions

New layered organic conductors, (BEDT-TTF)4(BiCl5)1 7 (1), δ-(BEDT-TTF)2BiCl5 (2), and δ-(BEDT-TTF)6Sb3Cl12 (3), were obtained (BEDT-TTF is bis(ethylenedithio)tetrathia-fulvalene). In the crystal structures of 1—3, organic radical cation layers are composed of di-merized stacks. The dimers are formed by BEDT-TTF radical cations rotated through angle ω relative to each other, which results in twisted stacks, giving rise to so-called twisted overlap mode in the layers. These layers alternate with non-conductive inorganic layers consisting of chains in which the Cl, Bi, and Sb sites are partially occupied. This indicates discontinuities in the chains of anions, and, apparently, the absence of continuous polymer chains in the crystal structure. According to measurements of the temperature dependence of the electrical resistance, the compounds are semiconductors.

Giant negative magnetoresistance and kinetic arrest of first-order ferrimagnetic-antiferromagnetic transition in Ge doped Mn2Sb

The effect of partial substitution of Ge for Sb on the first-order ferrimagnetic (FRI)–antiferromagnetic (AFM) transition in Mn2Sb has been studied. It shows that the transition temperature (Tt) can be tuned between 119 K and 271 K by substituting 2.5%–10% Ge at Sb sites in Mn2Sb. The variation of density of state at the Fermi level N(Ef) with Ge substitution shows that dN(E)/dE is positive at Ef in the AFM state. With the application of a magnetic field, Tt shifts to low temperature, which results in a giant negative magnetoresistance (MR) reaching a value of 70% for 2.5% substitution. Our results show that FRI to AFM transformation during cooling stops around 35 K, even though it remains incomplete. This, along with the nonmonotonic variation of lower critical field, open loop in isothermal MR, and increasing difference in zero field cooled warming and field cooled warming resistivity with increasing magnetic field, shows that the FRI to AFM transition is kinetically arrested in the case of 2.5% Ge substitution.

Achieving a High Thermoelectric Performance of Tetrahedrites by Adjusting the Electronic Density of States and Enhancing Phonon Scattering.

Recently, many researchers have focused on tetrahedrite-based compounds due to their intrinsic low thermal conductivity; however, their thermoelectric performance is limited by the lower power factor. In this case, using Ge doping on Sb sites, the power factor is obviously enhanced due to an increment in carrier concentration and density of states; simultaneously, the thermal conductivity is substantially suppressed by atomic defects. Also, ZnO nanoparticles are introduced in the Ge-doped compounds to further weaken the thermal conductivity. As a result, the maximum dimensionless figure of merit (ZT) of ∼1.0 is obtained for the Cu12Sb3.96Ge0.04S13-0.5 wt % ZnO sample at 750 K, which is ∼72% larger than that of Cu12Sb4S13. All results indicate that suitable elemental doping combined with the incorporation of the nanophase is a very promising approach for Cu12Sb4S13 tetrahedrites to improve the thermoelectric performance.

Effect of Sn Substitution on the Thermoelectric Properties of Synthetic Tetrahedrite.

The present study reports the effect of Sn substitution on the structural and thermoelectric properties of synthetic tetrahedrite (Cu12Sb4S13) system. The samples were prepared with the intended compositions of Cu12Sb4- xSn xS13 ( x = 0.25, 0.35, 0.5, 1) and sintered using spark plasma sintering. A detailed structural characterization of the samples revealed tetrahedrite phase as the main phase with Sn substituting at both Cu and Sb sites instead of only Sb site. The theoretical calculations using density functional theory revealed that Sn at Cu(1) 12d or Cu(2) 12e site moves the Fermi level ( EF) toward the band gap, whereas Sn at Sb 8c site introduces hybridized hole states near EF. Consequently, a relatively high optimum power factor of 1.3 mW/mK2 was achieved by the x = 0.35 sample. The Sn-substituted samples exhibited a significant decrease in the total thermal conductivity (κT) compared to the pristine composition (Cu12Sb4S13), primarily because of reduced electronic thermal conductivity. Due to an optimum power factor (1.3 mW/mK2) and reduced thermal conductivity (0.9 W/mK), a maximum zT of 0.96 at 673 K was achieved for x = 0.35 sample, which is nearly 40% increment compared to that of the pristine (Cu12Sb4S13) sample.

Negative Te spin polarization responsible for ferromagnetic order in the doped topological insulator V0.04(Sb1−xBix)1.96Te3

Ferromagnetic topological insulators have emerged as a promising platform for quantum anomalous Hall (QAH) effect with a dissipationless edge transport. However, the observation of QAH effect has so far been restricted to extremely low temperatures. We investigate the microscopic origin of ferromagnetism coupled with topological insulators in vanadium-doped (Sb, Bi)(2)Te-3 employing the x-ray magnetic circular dichroism, angle-resolved two-photon photoemission spectroscopy, combined with first-principles calculations. We found a negative spin polarization, and thus an antiparallel magnetic moment at the Te site with respect to that of the vanadium dopants, which plays the key role in the ferromagnetic order. We ascribe it to the hybridization between Te p and V d majority spin states at the Fermi energy (E-F), being supported by a Zener-type p-d exchange interaction scenario. The substitution of Bi at the Sb site suppresses the bulk ferromagnetism by introducing extra electron carriers in the majority spin channel of Te p states that compensates the antiparallel magnetic moment on the Te site. Our findings reveal important clues to designing magnetic topological insulators with higher Curie temperature that work under ambient conditions.

Thermoelectric transport properties of Ni-, Pd-, and Pt- doped skutterudites with S-filling as charge compensation

Unlike typical electronegative guest filled skutterudites, which are doped with electron donors at Sb sites to form thermodynamically stable compounds. In this study, substituting at Co sites with Ni, Pd, and Pt atoms instead of at the Sb sites was analyzed. The influence of Ni, Pd, and Pt on the electronic band structure of Ni-, Pd-, and Pt-doped skutterudites was thoroughly analyzed. The degree of band splitting caused by the doping elements was analyzed and shown to be correlated with the strength of anti-bonding between the doping elements and neighboring Sb atoms. The electronic structures in the conduction band minimum (CBM) of the S-filled skutterudites did not undergo a significant change when compared to those of the doped skutterudites. Therefore, the thermoelectric (TE) performance was optimized because of the reduction in the degree of energy band splitting due to the addition of elements ranging from Ni to Pt.

The effects of Ge occupation and hydrostatic pressure on the metamagnetic phase transition and magnetocaloric effect in Mn2Sb alloy

The effects of Ge occupations at Sb and Mn sites in Mn2Sb system had been re-examined along with the influence of hydrostatic pressure. The metamagnetic phase transition from ferrimagnetic (FRI) to antiferromagnetic (AFM) state was observed in Mn2Sb1-xGex (x = 0.05, 0.1) and (Mn1-yGey)2Sb (y = 0.025, 0.04) alloys. The phase transition temperature, Tt, was gradually increased with increased Ge substitution for both Sb and Mn, but slightly decreased under increased hydrostatic pressure in Mn2Sb0.95Ge0.05 alloy. Meanwhile, the slope of critical field as the function of temperature was reduced with increased hydrostatic pressure and Ge substitution amount in (Mn1-yGey)2Sb (y = 0.025, 0.04) alloys. For a field change of 7 T, the maxima of magnetic entropy changes of 6 Jkg-1K-1 and 7.1 Jkg-1K-1 have been achieved in Mn2Sb0.95Ge0.05 and Mn1.95Ge0.05Sb alloys, which are gradually decreased by more Ge substitution and increased hydrostatic pressure.

Interface-Driven Phase Transition of Phase-Change Material

In order to be able to control the phase transition of engineered phase-change materials, the specific understanding of phase transition processes is essential. To understand the effect of dopant on phase transition, the phase transition processes of Bi5.5(In3SbTe2)94.5 (Bi-IST) are quantitatively investigated with regard to the interfacial, bulk, entropy, and Gibbs free energies involved in the intermediate InSb and InTe phases and the crystallized Bi-IST. In the first step, InSb is crystallized; InTe and Bi are present in the amorphous phase. In the second step, heterogeneous nucleation of crystalline InTe occurs on the InSb. The energy barrier calculated for this nucleation of crystalline InTe is reduced by 1.5 times owing to the interfacial reaction of 5.5 atom % of Bi atoms compared to the case without Bi. In the third step, crystalline InSb and InTe are crystallized to Bi-IST since Bi atoms substitute Sb sites with a higher interfacial energy. The difference in the Gibbs free energy of the Bi-IST is −1.4 × 105 eV, which is lower than the −1.1 × 105 eV of the IST; this is because the differences in entropy with an increase in temperature and the interfacial energy are increased owing to the added Bi atoms. This lower Gibbs free energy becomes a driving force for the stable phase transition of Bi-IST at a lower transition temperature compared with that of the IST. With these phase transition processes, the contribution shares of enthalpy, entropy with temperature change, and interfacial energy are quantitatively analyzed; moreover, we recommend one of the various methods to design a novel phase-change material.

Joint effect of magnesium and yttrium on enhancing thermoelectric properties of n-type Zintl Mg3+δY0.02Sb1.5Bi0.5

N-type Mg3Sb2-based Zintl compounds have attracted considerable interest in recent years for their high thermoelectric performance. Mg3Sb2-based compounds inherently have p-type transport properties because of the presence of intrinsic Mg vacancies. Therefore, eliminating Mg vacancies and increasing the electron concentration are crucial for achieving high-performance n-type Mg3Sb2-based materials. The addition of excess Mg in the initial composition and the doping of chalcogens (Te, Se, and S) at the Sb site have been the primary methods used to date. Here, we demonstrate that n-type conduction was successfully achieved by a simple Y doping at the Mg site without adding extra Mg in the initial composition. Neutron diffraction analysis shows that Y preferentially goes to the Mg (Ⅱ) site and that almost all of the Mg vacancies are eliminated, giving rise to a strong donor effect to create n-type conduction. By eliminating the vacancies, the carrier concentration is easily optimized through the combination of Y and Mg, leading to a peak ZT of ∼1.8 at 773 K in Mg3.02Y0.02Sb1.5Bi0.5.

Li3SbO4 lithium-ion battery material: Defects, lithium ion diffusion and tetravalent dopants

Abstract Lithium antimony oxide, Li3SbO4, is a candidate anode material for rechargeable lithium ion batteries. Static atomistic scale simulations based on the classical pair potentials are employed to provide insights into the defect chemistry, doping behaviour and lithium diffusion paths in Li3SbO4. Here we show that, Li Frenkel is the dominant intrinsic defect process and the activation energy of Li diffusion is very low (0.21eV) suggesting that very high Li conduction is expected in this material. In particular, long range lithium diffusion paths via vacancy mechanism were constructed and it is confirmed that the lowest activation energy migration path is along the bc-axis plane with a zig-zag pattern. The calculations further suggest that cation anti-site defects, in which Li and Sb exchange their atomic positions, would not be observed with significant intrinsic concentration at operating temperatures. Subvalent doping by Si on the Sb site is energetically favorable suggesting that this efficient way to increase the Li content in Li3SbO4 should be stimulated experimentally. The electronic structure calculations based on the density functional theory (DFT) show that introduction of tetravalent dopants will not alter the band-gap significantly .

Enhanced thermoelectric properties of CoSb3-based skutterudites by filling Se as electronegative element

Filling electronegative guests into CoSb3-based skutterudites has been regarded as a promising way to improve their electrical and thermal transport properties. In this study, a series of SeyCo4-xPdxSb12-2ySe2y compounds have been prepared by traditional solid state reaction methods. Se as electronegative element was introduced into both the voids and the Sb sites of CoSb3-based skutterudite, and Pd was further introduced to stabilize Se in the voids. The phase compositions and electrical and thermal transport properties of the compounds have been investigated and the related mechanisms were explored. It is found that the forming of thermodynamically stable compounds is due to the charge compensation between the Pd and Se. By balancing the effect of the decrease of κL and the decrease of σ, the zT of Se0.2Co3.7Pd0.3Sb11.6Se0.4 sample amounted up to 0.88. With Te introduced into Se0.2Co3.7Pd0.3Sb11.6Se0.4 sample, the filling fraction of Se indeed increase by the charge-compensation effect of Pd and Te. And the zT of Se0.2Co3.7Pd0.3Te0.2Sb11.4Se0.4 sample was further improved to about 0.9.

High Thermoelectric Figure of Merit in p-Type (Bi2Te3)x − (Sb2Te3)1−x Alloys Made from Element-Mechanical Alloying and Spark Plasma Sintering

p-Type (Bi2Te3)x − (Sb2Te3)1−x alloys with high thermoelectric properties were fabricated for waste heat energy recovery by mechanical alloying followed by spark plasma sintering. The samples’ diffraction peaks, such as the (015) positions, were slightly shifted from high to low 2θ angles with decreasing Sb2Te3 content due to the occupation of Sb sites by Bi atoms in the crystal lattice. The electrical conductivity increased with (Sb2Te3) content due to an increase in carrier concentration. The sample with the nominal composition of (Bi2Te3)0.15 + (Sb2Te3)0.85 exhibited a maximum thermoelectric figure of merit, ZT of 1.3 ± 0.06 at 400 K, and 1.07 ± 0.06 at 300 K. This enhanced ZT was successfully achieved by increasing (Sb2Te3) content, which reduces intrinsic conduction at higher temperatures by increasing carrier concentration and band gaps. The enhanced thermoelectric performance of the (Bi2Te3)0.15 + (Sb2Te3)0.85 TE materials can provide exceptional benefits for power generation and cooling applications around 400 K.

The definition and crystal structure of clino-oscarkempffite, Ag15Pb6Sb21Bi18S72

Clino-oscarkempffite, Ag 1.27 Pb 0.49 Sb 1.68 Bi 1.54 S 6.01 , idealized as Ag 1.25 Pb 0.5 Sb 1.75 Bi 1.5 S 6 ( Z = 12), from the Colorada vein, Animas mine, Chocaya Province, Department of Potosi, Sur Chichas, Bolivia, is an N = 4 member of the lillianite homologous series, oversubstituted according to the Ag + (Bi, Sb) ↔ 2Pb substitution to 122.8% in comparison to the formula of gustavite, AgPbBi 3 S 6 . Optical properties of clino-oscarkempffite are very similar to those of oscarkempffite and other Bi (Bi–Sb) lillianite homologues. Reflectance values in air vary between 47.5 and 35.2%. Hardness was evaluated to 3–3½, based on VHN 50 range 189–208, mean 200 kg mm −2 . Density was calculated to 6.04 g cm −3 . Minerals associated with clino-oscarkempffite are aramayoite, oscarkempffite, arsenopyrite, ferrokesterite, freibergite, miargyrite, pyrite and quartz. Clino-oscarkempffite is monoclinic, lattice parameters a 39.811(25) A, b 19.280(12) A, c 8.278(5) A, β 96.195(9)°, V 6316.7 A 3 , space group P 2 1 / c . It is a three-fold superstructure of the lillianite aristotype, with a doubled 4 A axis and, uniquely, a tripled ∼13.3 A a parameter. In the crystal structure, configured as a general N = 4 lillianite homologue, the central octahedra of the PbS-like slabs are mixed (Bi,Sb), (Sb,Bi) and Sb sites in alternation along the 8.3 A direction, whereas in the marginal coordination octahedra (Sb,Bi) positions alternate with distorted tetrahedral coordinations of Ag. The bicapped trigonal coordination prisms on meeting planes of two octahedral slabs are occupied by mixed (Pb,Bi) sites. Cation occupation schemes result in blocks with monoclinic overall symmetry which alternate along [1 0 0] with blocks with orthorhombic overall symmetry. The order–disorder implications of this division are discussed in the paper.

CARBON AND NUTRIENT LOSSES THROUGH BIOMASS BURNING, AND LINKS WITH SOIL FERTILITY AND YAM (DIOSCOREA ALATA) PRODUCTION

SUMMARYBiomass burning has links with a number of global concerns including soil health, food security and climate change. In central Côte d'Ivoire (West Africa), we conducted a field study to compare nutrient losses, soil fertility and yam yield in slash-and-burn versus slash-and-mulch agriculture. Trials involved five sites established in the dominant Chromolaena odorata fallows of the region, each consisting of paired plots: slash and burnt biomass (SB) versus slashed and unburnt biomass, but left to serve as mulch (SM). Carbon and five elemental nutrients were assessed in the aboveground biomass prior to burning and in ash after fires; losses were assessed by subtraction. The greatest proportions of loss occurred with C (95%), N (95%) and K (74%), corresponding to losses into the atmosphere of 3532 ± 408, 200 ± 36, 132 ± 36 kg ha−1. Six weeks after the fire, soil properties were assessed: soil organic C, total N and Mg2+ were higher in SM than in SB sites. At final harvest, yam tuber yield was twice as large in SM as in SB (18 ± 4 vs. 9 ± 2 Mg ha−1) with soil C, total N and K+ as the main influential soil parameters. The key finding was that the elements lost in greatest proportion during burning were those mostly influencing yam yields. Because a clear negative relationship between biomass burning and yam production has been established the promotion of the more productive, alternate slash-and-mulch system compared to slash-and-burn system, is warranted. The findings of our research can be used in support of developing a sustainable yam production system in the region and in West Africa more generally.

Evolution and dynamics of the pandemic H1N1 influenza hemagglutinin protein from 2009 to 2017.

The emergence of swine-origin pandemic H1N1 (pH1N1) in 2009 invigorated extensive surveillance programs worldwide which have resulted in the deposition of large numbers of H1N1 sequences to Genbank. In the present study, we report on global evolution and dynamics of the pandemic H1N1 influenza Hemagglutinin (HA) protein in viruses isolated from three different continents (North America, Europe and Asia) during the period between April 2009 until April 2017. Close to 2000 HA full protein sequences were downloaded from the Influenza Research Database of the NCBI and analyzed using DNAStar to run an alignment, the web-based NetNglyc to predict N-Glycosylation sites and finally, the BEAST software package to calculate evolution and substitution rates. Our analysis improves upon other published papers in that we report on frequencies, dynamics and impact of HA mutations in pH1N1 viruses isolated from three continents during the past decade, as well as the evolution rate and site-specific selection pressures. Sequence based analysis demonstrated substantial changes in the HA protein over the last decade. Results showed that the HA gene is under negative selection (P value; HA= -2.253). The evolution rates varied among the three continents ranging from 2.36 × 10-3 in Europe to 3.18 × 10-3 in Asia. Mutations were detected at higher frequency and faster rate at the antigenic sites surrounding the receptor-binding domain (RBD), in particular, in the Sa and Sb sites. Mutations were either gradually accumulated to become fixed in currently circulating strains (D114N, S179N, S202T, S220T, I233T, K300E and E391K) or dynamic in terms of appearance and disappearance, both spatially and temporally (A203T, N458K and E508G). Some of the reported mutations have been shown to increase infection severity (D239G/N; globular head), enhance HA binding affinity to its receptor (S200P and S202T; RBD), or have deleterious effect on HA function (N458K and E508G; stem region). The continuous accumulation of mutations at the Sa site led to the gradual acquisition of glycosylation at residue 179 starting from 2015, which became a dominant feature in all strains isolated in the following years. In addition to sharing common amino acid substitutions (e.g. S179N in HA head and E516K in HA stem) with previous seasonal strains, the pattern of glycosylation acquisition/loss at 177 and 179 positions on the globular head, which are prominent features of immune escape, implicate that pH1N1 might follow a similar evolution trend as the SC1918 pandemic virus.