Structure and Transport Properties in Itinerant Antiferromagnet RE2(Ni1-xCu x)5As3O2 (RE = Ce, Sm)

Article abstract of DOI:10.1021/acs.inorgchem.8b03360

We report the crystal structure and physical properties of two Ni₅As₃-based compounds RE₂Ni₅As₃O₂ (RE = Ce, Sm). The former exhibits structural phase transition from tetragonal (space group I4/mmm, 139) to orthorhombic (space group Immm, 71) symmetry at 230 K, while the latter undergoes a charge-density-wave-like structural distortion with abrupt change of Ni-As bond length. Both compounds show antiferromagnetic transitions due to RE³⁺ ions ordering at 4.4 and 3.4 K, accompanying with the large enhancement of Sommerfeld coefficients comparing to the nonmagnetic La analogue. Although the Cu substitution for Ni induces structural anomalies and suppression of structural transition like the behaviors in La/Pr/Nd analogues, the superconductivity is not observed in both Cu-doped RE₂Ni₅As₃O₂ (RE = Ce, Sm) above 0.25 K. Our structural refinements reveal that the lacking of superconductivity in RE₂(Ni_1-xCu_x)₅As₃O₂ might relate to the anomalous increase of As height, h₁.

Full text of DOI:10.1021/acs.inorgchem.8b03360

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Structure and Transport Properties in Itinerant Antiferromagnet
RE2(Ni1−xCux)5As3O2 (RE = Ce, Sm)
Xu Chen,†,‡ Jian-gang Guo,*,†,§ Chunsheng Gong,† Erjian Cheng,∥ Yanpeng Song,†,‡ Tianping Ying,∥
Jun Deng,†,‡ Shiyan Li,∥,# and Xiaolong Chen*,†,§
†Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603,
Beijing 100190, China
‡University of Chinese Academy of Sciences, Beijing 100049, China
§Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
∥State Key Laboratory of Surface Physics, Department of Physics, and Laboratory of Advanced Materials, Fudan University,
Shanghai 200433, China
#Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
S
* Supporting Information
ABSTRACT: We report the crystal structure and physical properties of
two Ni5As3-based compounds RE2Ni5As3O2 (RE = Ce, Sm). The former
exhibits structural phase transition from tetragonal (space group I4/mmm,
139) to orthorhombic (space group Immm, 71) symmetry at 230 K, while
the latter undergoes a charge-density-wave-like structural distortion with
abrupt change of Ni−As bond length. Both compounds show
antiferromagnetic transitions due to RE3+ ions ordering at 4.4 and 3.4 K,
accompanying with the large enhancement of Sommerfeld coefficients
comparing to the nonmagnetic La analogue. Although the Cu substitution
for Ni induces structural anomalies and suppression of structural transition
like the behaviors in La/Pr/Nd analogues, the superconductivity is not
observed in both Cu-doped RE2Ni5As3O2 (RE = Ce, Sm) above 0.25 K.
Our structural refinements reveal that the lacking of superconductivity in
RE2(Ni1−xCux)5As3O2 might relate to the anomalous increase of As height,
h1.
elongating the bond length of (Ch2)2− dimer could
significantly enhance the Tc and change the crystal structure.
For example, in pyrite-type IrxSe2, increasing Ir content can
INTRODUCTION
■
Identifying the key structural unit and tuning its geometry are
important in exploring superconductor and understanding the
relationship between superconductivity (SC) and crystal
structure. One known example is FeAs-based superconductors,
lengthen the bonds of Se−Se and simultaneously influence the
Tc.11,12 The maximal Tc of 10 K can be reached as the weakest
Se−Se bonding states and the structural instability emerges.11
in which the distorted degree of FeAs4 tetrahedral empirically
Similarly, the breaking of Te−Te bonds in AuTe2 by chemical
determines the highest superconducting critical temperature
(Tc), magnetism, and correlation strength.1−3 Replacing the
substitution and physical pressure could induce SC accompany
with a phase transition.13,14 Furthermore, As−−As− zigzag
La2O2 layer by Sm2O2 can effectively enhance the Tc from 26
15,16
to 58.1 K by optimizing the FeAs4 tetrahedral geometry.4−7
Actually, the inherent mechanism is mainly tuning an indirect
hybridization degree of Fe dxz/dyz orbital and As pz orbital,
which can make the regular shape of FeAs4 tetrahedral (Fe−
As−Fe angle: 109.5°; As height:1.38 Å) have optimal electron-
correlation strength and hopping exchanges.
chain and As−As dimer are observed in Ca1−xLaxFe2As2
and Pt−CaFe2As2,17,18 respectively, which are critical to
stabilize the crystal and SC.
Very recently, three series of RE2(Ni1−xCux)5As3O2 (RE =
La, Pr, Nd) superconductors were discovered by us,19 in which
a Ni5As3 unit composed of antifluorite Ni2As2 layer and two
As−As dimer is believed to be the critical ingredient for SC. It
is found that Cu doping could enhance the Tc to 2.5 K. It
offers an opportunity to study the evolution of Ni5As3 unit and
SC through tuning the geometry of NiAs4 polyhedral and As
Besides, the anionic cluster of (Ch2)2− (Ch = Se, Te) and
(Pn2)4− (Pn = P, As) can be viewed as novel carrier controlling
unit,8−10 in which the main group elements are connected by
covalent bond. Altering the bond length can change the total
electron numbers and structural stability, which synergistically
influences the carrier concentration and electron−phonon
coupling strength. Previous experiments demonstrated that
Received: December 3, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
height. In this work, we report that the structure and properties
of two analogous RE2(Ni1−xCux)5As3O2 (RE = Ce, Sm), which
exhibit structural transition or charge-density-wave-like dis-
tortion under low temperatures. Through Cu doping, however,
the SC is not observed as low as 0.25 K in all measured
samples. Combing the crystallographic parameters in all five
RE2(Ni1−xCux)5As3O2 compounds, the evolution of Ni5As3
unit has been systemically investigated, and the optimal
geometry of Ni5As3 unit is identified.
EXPERIMENTAL SECTION
■
Polycrystalline samples of RE2(Ni1−xCux)5As3O2 (x = 0.0−1.0) were
synthesized by solid-state reactions. The binary precursors CeAs/
SmAs, Cu3As and NiAs were presynthesized by reacting Ce/As filings,
Cu, Ni, and As powders at 1000 K for 20 h. Then, the powders of
CeAs/SmAs, Cu3As, NiAs, La2O3/Sm2O3, Ni and Cu were weighted
as the stoichiometric ratio, ground and pelleted under a pressure of 15
MPa in an argon-filled glovebox. The pellets were loaded into an
Al2O3 crucible and sealed into evacuated silica tube, which was heated
up to 1250 K and kept for 40 h. The powder X-ray diffraction
(PXRD) pattern was collected at room temperature using a
Panalytical diffractometer (Cu Kα radiation) equipped a low-
temperature option (10−300 K). Rietveld refinements were
performed using Fullprof suites.20 The electrical resistivity (ρ), dc
magnetic susceptibility (χ), and heat capacity (Cp) were measured
through the standard four-wire method, vibrating sample magneto-
meter and heat relaxation method at PPMS (Quantum Design),
respectively. The resistance below 1.8 K was measured in an Oxford
fridge equipped with a dilution refrigerator and a He-3 probe. Crystal
orbital Hamilton population (COHP) analysis as implemented in the
LOBSTER package21,22 gives information about the interatomic
interaction, where a negative (positive) COHP value indicates
bonding (antibonding) states.
Figure 1. Rietveld refinements of powder X-ray pattern of
Ce2Ni5As3O2 (a) and Sm2Ni5As3O2 (b) collected at 300 K. The
inset of (a) is crystal structure of RE2Ni5As3O2.
(C4−C2). The inset of Figure 2b shows the schematic structure
of Ni4As unit at 10 K. The Ni−Ni square plane changed into
distorted Ni4As polyhedral with two upshifted Ni(1) and two
downshifted Ni(2). In Figure 2c, we found that the (105) and
(200) peaks split into (015)/(105) and (020)/(200) peaks
below 220 K. The resultant lattice constants are shown in
Figure 2d. It can be seen that the symmetry breaking and the
abrupt changes in c and volume (V) clearly evidence a
structural phase transition as temperature going through 230
K.
RESULTS AND DISCUSSION
■
Figure 1a,b shows the Rietveld refinements of PXRD pattern of
RE2Ni5As3O2 (RE = Ce, Sm) collected at 300 K, respectively.
The calculated profiles are based on the initial model
RE2Cu5As3O2.19 Two refinements converged to Rp = 2.17%
and Rwp = 3.00%, Rp = 1.99% and Rwp = 2.76%, respectively,
indicating the reliable structural determination. The lattice
constants of Ce2Ni5As3O2 are a = b = 4.0360(1) Å, c =
22.3686(5) Å with space group I4/mmm (No. 139), and those
of Sm2Ni5As3O2 shrink to a = b = 3.9738(1) Å, c = 22.3053(6)
Å due to the smaller ion radius of Sm3+.23,24 The crystal
structure of RE2Ni5As3O2 (RE = Ce, Sm) are drawn as inset of
Figure 1a, which is consisted of fluorite-type RE2O2 layer and
Ni5As3 unit. The Ni5As3 can be viewed as conjunction of two
antifluorite Ni2As2 layers through Ni−Ni metallic bonds (2.60
Å). Here, the As(1)−As(2) distances along the c-axis (2.68 and
2.73 Å) locate the bonding regime of As−As covalent bonds,
and the As(1)−As(2) bond length determines the thickness of
Ni5As3 unit along c-axis.
The temperature-dependent magnetic susceptibility (χ−T)
of Ce2Ni5As3O2 is plotted at Figure 3a. The structural-
transition induces a small drop in 1/χ at 230 K. The data from
80 to 210 K can be well fitted by modified Curie−Weiss
equation 1/χ =(T − θ)/C, where C is a materials-specific Curie
constant and θ is Curie temperature. The estimated magnetic
moment is ∼2.94 μB and θ = −27 K, indicating an AFM
interaction due to RE3+ ions ordering, which is often observed
in the layered compounds with [RE2O2]2+ layers.24 A little
downward in χ(T) curve is found below ∼4.2 K, which is a
hint of AFM transition. In Figure 3b, we plotted the specific
heat (Cp) of Ce2Ni5As3O2 from 270 to 2.0 K, in which a sharp
peak shows up at 230 K, perfectly matching the temperature of
phase transition. The sharp peak indicates that it is a first-order
transition. Furthermore, fitting of low-temperature data using
the equation Cp/T = γ + βT2 + ηT4 gives Sommerfeld
coefficient (γ) is 93.6 mJ/mol K2, β = 1.18 mJ/mol K4, and η =
1.8 × 10−4 mJ/mol K6. The Debye temperature (ΘD) is
The temperature-dependent electrical resistivity (ρ-T) of
Ce2Ni5As3O2 is plotted in Figure 2a. It shows typical metallic
behavior, where two resistivity kinks at Ts = 230 K and TN =
4.4 K are observed. The former is associated with the structural
phase transition like the observation in ref 19, and the latter is
believed to be an antiferromagnetic transition of Ce3+ ion. To
check the structural phase transition, we measured the low-T
PXRD patterns of Ce2Ni5As3O2 from 300 to 10 K (see Figure
S1). Figure 2b shows the Rietveld refinements of PXRD profile
of Ce2Ni5As3O2 at 10 K, in which the structure symmetry
lowers to Immm (No. 71) with a0 = 4.0315(1) Å, b0 = 4.0608
(1) Å and c = 22.1875 (2) Å, exhibiting a rotation breaking
estimated to be 270.2 K as the equation ΘD = (12π4nR/5β)1/3
.
Meanwhile, we noted there is a large upturn of Cp(T) below 5
K, which is attributed to AFM ordered transition of Ce 4f
electron spin rather than that of Ni.25,26 The extrapolated γ(0)
of 0 K is about 15 J/(mol K), which comes from the strong
interaction of Ce 4f and Ni 3d electron.
B
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. (a) Electrical resistivity (ρ) of Ce2Ni5As3O2 as a function of temperature from 2 K-300 K. Inset is the ρ(T) data in lower-temperature
range. (b) Rietveld refinements of powder X-ray pattern of Ce2Ni5As3O2 collected at 10 K. Inset is the distortion of Ni4As polyhedral below Ts. (c)
Splitting of (105) and (200) peaks at different temperature. (d) Temperature-dependent lattice constants of Ce2Ni5As3O2.
that the Fermi surface is dominated by electrons after this
transition. Similarly, the PXRD pattern at 10 K of
Sm2Ni5As3O2 is refined to check the insight of resistivity
jump (see Figure S2). Figure 4b is the Rietveld refinements
profile of Sm2Ni5As3O2. In contrast to that of Ce2Ni5As3O2,
this pattern is still well-refined by a tetragonal unit cell (space
group: I4/mmm) without lowering rotation symmetry. The
whole fitting converged to Rwp = 4.59% and Rp = 3.04%. In
Figure 4c, upon cooling, the lattice constant, a, monotonously
decreases, while c increases and tends to saturate below 150 K,
showing a small kink at 80 K. This anomalous variation in
lattice constants is totally different from what happened in the
RE2TM5As3O2 (TM = Cu, Ni).19 Carefully examining the low-
temperature structure, we found that an increase of c, 0.05%, is
mainly attributed to the increase of As(1)−As(2) bond length
(1.3%), see Figure 4d. Actually, in the Ni5As3 unit, the two
kinds of anion height (h1 and h2) show inversed trend by
cooling, i.e., the upper h1 increases and the lower h2 decreases
(see Figure S3). It means that the value of coordination of
zNi(1) will continuously decrease, what perfectly matches our
Rietveld refinements as shown in Figure 4e,f. Furthermore,
there is an abrupt drop of zNi(1) at 80 K, which is believed to be
a kind of weak charge-density-wave-like transition as
observation in KNi2S2.27
Figure 3. (a) Temperature-dependent magnetic susceptibility and the
fitting results of Ce2Ni5As3O2. (b) The specific heat (Cp) of
The temperature-dependent magnetic susceptibility (χ−T)
Ce2Ni5As3O2 from 270 to 2 K. The insets show expanded view and
of Sm2Ni5As3O2 is plotted at Figure 5a. A clear AFM transition
the fitting curve in low-temperature range.
has been detected at TN = 4.11 K, which confirms that the
increase of ρ(T) is due to formation of magnetic ordering of
Sm3+ ions. The 1/χ−T data is fitted by modified Curie−Weiss
The ρ−T curve of Sm2Ni5As3O2 is shown in Figure 4a.
equation, yielding magnetic moment (μeff) is ∼1.21 μB and θ =
−15 K. The scale of μeff is slight smaller than the theoretical
value of free Sm3+ ions. In Figure 5b, we plotted the specific
heat (Cp) of Sm2Ni5As3O2 from 120 to 2.0 K. We did not see
any anomaly around T* = 80 K. In the lower temperature
Besides the metallic behavior, we observe a large jump of
resistivity at T* = 80 K and small increase at TN = 4.05 K. The
hysteresis of jump implies that it is a first-order transition.
Meanwhile, the Hall coefficient (RH), shown as inset of Figure
4a, changes from positive to negative below ∼80 K, indicating
C
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 4. (a) Electrical resistivity (ρ) of Sm2Ni5As3O2 as a function of temperature from 2 to 300 K. Inset is the temperature dependence of Hall
coefficient RH(T). (b) Rietveld refinements of powder X-ray pattern of Sm2Ni5As3O2 collected at 10 K. (c) and (d) Temperature-dependent lattice
constants and As(1)−As(2) bond lengths of Sm2Ni5As3O2. (e) Schematic evolution of NiAs fragment below 80 K. (f) Temperature-dependent
atomic site of zNi(1)
.
mJ/mol K2, β = 1.97 mJ/mol K4, and η = 3.1 × 10−4 mJ/mol
K6. Adding the contribution of ηT4 can better fit the data,
implying that small anharmonic effect due to anisotropic
bonding states may exist. The Debye temperature (ΘD) is
estimated to be 228.3 K as the equation ΘD = (12π4nR/5β)1/3
,
which is a little smaller that of Ce2Ni5As3O2. These
observations are like the behaviors of Kondo lattice reported
in CeRuPO28,29 and RENiAsO,24 where the local criticality of
4f electrons mainly determine the intrinsic properties.
We prepared a series of Cu-doped RE2Ni5As3O2 samples to
investigate the structure variation and superconductivity. The
PXRD patterns and structural information is shown in Figures
S4 and S5 and Table S1. Figure 6 presents the structural
evolution of Cu-doped RE2Ni5As3O2 samples and the results
are analogous to those of superconducting (La, Pr,
Nd)2(Ni1−xCux)5As3O2 (x = 0.0−1.0). The a-lattice increases,
while the c-lattice slightly decreases as x < 0.6. Once x > 0.6,
the a-lattice decreases, while the c-axis rapidly increases, see
Figure 6a,b. Figure 6c displays that the minima of c/a ratios
show up at x = 0.6, where these minima are close to 5.45. Even
though there are anomalies in lattice constants, the volumes of
unit cell linearly increase by 3.6 and 4.2%, respectively, as
shown in Figure 6d. Overall, the structural trend against Cu
doping is similar to that of full solid solutions of
La2(Ni1−xCux)5As3O2. However, the single-phase limits of
solid solutions are 90 and 80% for Cu-doped Ce2Ni5As3O2 and
Sm2Ni5As3O2, respectively.
Figure 5. (a) Temperature-dependent magnetic susceptibility and the
fitting results of Sm2Ni5As3O2. (b) Specific heat (Cp) of Sm2Ni5As3O2
from 120 to 2 K. Insets show the low-temperature Cp and Cp/T vs T
and their fitting curves.
Since the coordination environment of Ni and As is similar
to that of FeAs-based superconductors, we summarize the Ni−
As bond lengths, bond angles (Ni−As−Ni), and As height in
the (Ni/Cu)5As3 unit of RE2(Ni1−xCux)5As3O2 (RE = Ce, Sm)
compounds. The structure of (Ni/Cu)As plane in ac-plane is
range, a well-defined peak has been observed at 3.37 K, which
is consistent with the temperature of AFM ordering of Sm3+
ions. Fitting the low-temperature data using equation, Cp/T =
γ + βT2 + ηT4, yields the Sommerfeld coefficient (γ) is 362.7
D
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 6. Lattice constants a, c, c/a ratio, and V of RE2(Ni1−xCux)5As3O2 as a function of Cu content.
Figure 7. Cu-content-dependent Ni(1)−As(1) bond length (a), Ni(1)−As(1)−Ni(1) angle 1 (b), As height (h1) (c), and As(1)−As(2) distance
(d) in RE2(Ni1−xCux)5As3O2. Inset is structure of central CuAs fragment along c-axis.
shown in the inset Figure 7a. The anion heights (h1 and h2) are
not identical due to different Wyckoff position of As(1) and
As(2), which are synergistically determined by the Ni−As
bond length and angles 1 and 2, respectively. From Figure 7a,
one can see that the Cu doping slightly changes the Ni(1)−
As(1) bond length x < 0.6, while it abruptly elongates the
Ni(1)−As(1) bond lengths once x > 0.6. For
Sm2(Ni1−xCux)5As3O2, the Cu-doping mildly increase this
bond length in whole doping range. For angle 1, see Figure 7b;
the Cu-doping straightly increases the value, while the trend is
inversed as x > 0.6. As for the anion height h1, it first decreases
as x < 0.6 and then drastically increases; see Figure 7c.
However, h2 monotonously increases in the whole range of Cu
doping; see Figure S6. The distinct trends of h1 and h2 induce
that the As(1)−As(2) distance initially increases and then
rapidly increases once the x is above 0.6, as shown in Figure
7d. As in previous reports,10 the As−As covalent bond length is
around 2.7−2.9 Å. As x > 0.8, both As−As distances are above
E
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
2.85 Å, leading to a rather weak bonding state. It means that
the As−As bond gradually breaks against Cu doping. In
La2(Ni1−xCux)5As3O2, the As−As bond lengths are smaller
than 2.80 Å, where the bonding states are stable. However, as
the calculation of molecular COHP, the Fermi level is just
below the antibonding states. The As−As bonding energy are
3.01 and 2.66 eV per bond for Ce2Ni5As3O2 and Sm2Ni5As3O2,
respectively; see Figure S7. Doping Cu would naturally upshift
the Fermi level to the antibonding states of As−As bond,
destabilizing the structure.
the ideal values (1.38 Å and 109.5°) in FeAs-superconductors.
Although the Cu substitution in antiferromagnetic (Ce/
Sm)2(Ni1−xCux)5As3O2 could realize the more regular (Ni/
Cu)As4 tetrahedral, the SC is absent. From this point of view,
the findings in Cu-doped RE2Ni5As3O2 apparently do not obey
those empirical rules in FeAs-based superconductors. It
provides a new perspective to fully understand the TM-based
oxypnictides superconductors.
ASSOCIATED CONTENT
■
Figure 8 is electrical resistivity of RE2(Ni1−xCux)5As3O2 (RE
= Ce, Sm) samples. Most samples show metallic behaviors, and
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.8b03360.
Crystallographic parameters, PXRD patterns, −COHP
(PDF)
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: jgguo@iphy.ac.cn.
*E-mail: xlchen@iphy.ac.cn.
ORCID
Xu Chen: 0000-0003-3477-2204
Jian-gang Guo: 0000-0003-3880-3012
Xiaolong Chen: 0000-0001-8455-2117
Notes
The authors declare no competing financial interest.
Figure 8. Temperature-dependent electrical resistivity (ρ) of
Ce2(Ni1−xCux)5As3O2 and Sm2(Ni1−xCux)5As3O2. Insets are ρ(T)/
ρ(3 K) for x = 0.6 samples from 0.25 to 3 K.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (No. 51772322 and 51532010), the
National Key Research and Development Program of China
(No. 2017YFA0304700 and 2016YFA0300600), and the
Strategic Priority Research Program and Key Research
Program of Frontier Sciences of the Chinese Academy of
Sciences (No. XDB07020100 and QYZDJ-SSW-SLH013).
the resistivity jump due to phase transition in
RE2(Ni1−xCux)5As3O2 is quickly suppressed by Cu doping.
However, the low-temperature anomalies associated with AFM
transition are still observed in Ce2(Ni1−xCux)5As3O2. Unfortu-
nately, we did not see any superconductivity above 0.25 K in
all measured samples, contrasting the findings in La/Pr/
Nd2(Ni1−xCux)5As3O2 samples.
REFERENCES
■
As we know, in the FeAs-based superconductors, the optimal
h1 and Fe−As−Fe angle 1 are 1.38 Å and 109.5°, respectively.
Lowering (elevating) the h1 would increase (decrease) the
orbital hybridization and drive the system to more itinerant
(localized) states, leading to suppression of Tc.30 In the Ni5As3
unit, h1 (1.17−1.31 Å) is apparently smaller than 1.38 Å, and
angle 1 (115−120°) is larger than the empirically optimal value
(109.5°), which may be the origin of itinerant states and lower
Tc. However, we note that the h1 and angle 1 in Ni5As3 are
comparable to the counterparts of h1 (1.13 and 1.15 Å) and
the Ni−As−Ni angle (122.9 and 121.9°) in superconducting
AeNi2As2 (Ae = Sr, Ba; Tc = 0.7 and 0.6 K) and LaNiAsO (2.4
K).31−33 For La2(Ni1−xCux)5As3O2 superconductors, the
sample with optimal Tc of 2.5 K has the smallest h1 (1.15 Å)
and the largest angle 1 (120.9°) at x = 0.6. Its h1 can be easily
tuned by Cu doping or changing RE3+ ions. Through Cu-
doping, h1 increases, and angle 1 decreases, which lower the Tc.
Similarly, replacing the RE3+ ions by Sm3+ elevates the h1,
which also can explain the reason for suppressing Tc.
(1) Lee, C. H.; Iyo, A.; Eisaki, H.; Kito, H.; Fernandez-Diaz, M. T.;
Ito, T.; Kihou, K.; Matsuhata, H.; Braden, M.; Yamada, K. Effect of
structural parameters on superconductivity in fluorine-free LnFeA-
sO1‑y (Ln = La, Nd). J. Phys. Soc. Jpn. 2008, 77, No. 083704.
(2) Zhao, J.; Huang, Q.; de la Cruz, C.; Li, S. L.; Lynn, J. W.; Chen,
Y.; Green, M. A.; Chen, G. F.; Li, G.; Li, Z.; Luo, J. L.; Wang, N. L.;
Dai, P. C. Structural and magnetic phase diagram of CeFeAsO1−xFx
and its relation to high-temperature superconductivity. Nat. Mater.
2008, 7, 953.
(3) Zhang, C. L.; Harriger, L. W.; Yin, Z. P.; Lv, W. C.; Wang, M. Y.;
Tan, G. T.; Song, Y.; Abernathy, D. L.; Tian, W.; Egami, T.; Haule,
K.; Kotliar, G.; Dai, P. C. Effect of pnictogen height on spin waves in
iron pnictides. Phys. Rev. Lett. 2014, 112, 217202.
(4) Kamihara, Y.; Watanabe, Y. T.; Hirano, M.; Hosono, H. Iron-
based layered superconductor La[O1‑xFx]FeAs (x = 0.05−0.12) with
Tc = 26 K. J. Am. Chem. Soc. 2008, 130, 3296.
(5) Ren, Z. A.; Lu, W.; Yang, J. W.; Yi, X.; Xiao-Li, S.; Zheng-Cai;
Guang-Can, C.; Shen, L.; Li, Z. C.; Che, G. C.; Dong, X. L.; Sun, L.
L.; Zhou, F.; Zhao, Z. X. Superconductivity at 55K in iron-based F-
doped layered quaternary compound Sm[O1‑xFx]FeAs. Chin. Phys.
Lett. 2008, 25, 2215.
(6) Chen, X. H.; Wu, T. G.; Wu, R.; Liu, H.; Chen, H.; Fang, D. F.
Superconductivity at 43 K in SmFeAsO1‑xFx. Nature 2008, 453, 761.
(7) Fujioka, M.; Denholme, S. J.; Ozaki, T.; Okazaki, H.; Deguchi,
K.; Demura, S.; Hara, H.; Watanabe, T.; Takeya, H.; Yamaguchi, T.;
Kumakura, H.; Takano, Y. Phase diagram and superconductivity at
CONCLUSION
■
In summary, detailed structure analyses reveal there is optimal
(Ni/Cu)As4 geometry with As height (1.15 Å) and angle 1
(121.6°) for SC in La2(Ni1−xCux)5As3O2, which are far from
F
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
58.1 K in α-FeAs-free SmFeAsO1−xFx. Supercond. Sci. Technol. 2013,
26, No. 085023.
(26) Jesche, A.; krellner, C.; de Souza, M.; Lang, M.; Geibel, C. Rare
earth magnetism in CeFeAsO: a single crystal study. New J. Phys.
2009, 11, 103050.
(27) Neilson, J. R.; McQueen, T. M.; Llobet; Wen; Suchomel.
Charge density wave fluctuations, heavy electrons, and super-
conductivity in KNi2S2. Phys. Rev. B: Condens. Matter Mater. Phys.
2013, 87, No. 045124.
(8) Qi, Y. P.; Matsuishi, S.; Guo, J. G.; Mizoguchi, H.; Hosono, H.
Superconductivity in defective pyrite-type iridium chalcogenides
IrxCh2 (Ch = Se and Te). Phys. Rev. Lett. 2012, 109, 217002.
(9) Hirai, D.; Von Rohr, F.; Cava, R. J. Emergence of super-
conductivity in BaNi2(Ge1−xPx)2 at a structural instability. Phys. Rev.
B: Condens. Matter Mater. Phys. 2012, 86, 100505.
(10) Jia, S.; Jiramongkolchai, P.; Suchomel, M. R.; Toby, B. H.;
Checkelsky, J. G.; Ong, N. P.; Cava, R. J. Ferromagnetic quantum
critical point induced by dimer-breaking in SrCo2(Ge1−xPx)2. Nat.
Phys. 2011, 7, 207.
(28) Krellner, C.; Kini, N. S.; Bruning, E. M.; Koch, K.; Rosner, H.;
̈
Nicklas, M.; Baenitz, M.; Geibel, C. CeRuPO: A rare example of a
ferromagnetic Kondo lattice. Phys. Rev. B: Condens. Matter Mater.
Phys. 2007, 76, 104418.
(29) Kitagawa, S.; Ishida, K.; Nakamura, T.; Matoba, M.; Kamihara,
Y. Ferromagnetic quantum critical point in heavy-fermion iron
oxypnictide Ce(Ru1−xFex)PO. Phys. Rev. Lett. 2012, 109, 227004.
(30) Kuroki, K.; Usui, H.; Onari, S.; Arita, R.; Aoki, H. Pnictogen
height as a possible switch between high-Tc nodeless and low-Tc nodal
pairings in the iron-based superconductors. Phys. Rev. B: Condens.
Matter Mater. Phys. 2009, 79, 224511.
(31) Ronning, F.; Kurita, N.; Bauer, E. D.; Scott, B. L.; Park, T.;
Klimczuk, T.; Movshovich, R.; Thompson, J. D. The first order phase
transition and superconductivity in BaNi2As2 single crystals. J. Phys.:
Condens. Matter 2008, 20, 342203.
(32) Bauer, E. D.; Ronning, F.; Scott, B. L.; Thompson, J. D.
Superconductivity in SrNi2As2 single crystals. Phys. Rev. B: Condens.
Matter Mater. Phys. 2008, 78, 172504.
(33) Watanabe, T.; Yanagi, H.; Kamihara, Y.; Kamiya, T.; Hirano,
M.; Hosono, H. Nickel-based layered superconductor, LaNiOAs. J.
Solid State Chem. 2008, 181, 2117−2120.
(11) Guo, J. G.; Qi, Y. P.; Matsuishi, S.; Hosono, H. Tc maximum in
solid solution of pyrite IrSe2−RhSe2 induced by destabilization of
anion dimers. J. Am. Chem. Soc. 2012, 134, 20001.
(12) Guo, J. G.; Qi, Y. P.; Hosono, H. Structure and super-
conductivity in pyrite Ir0.95−xRhxTe2: A comparison with analogous
selenides. Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 87, 224504.
(13) Kudo, K.; Ishii, H.; Takasuga, M.; Iba, K.; Nakano, S.; Kim, J.;
Fujiwara, A.; Nohara, M. Superconductivity induced by breaking Te2
dimers of AuTe2. J. Phys. Soc. Jpn. 2013, 82, No. 063704.
(14) Kitagawa, S.; Kotegawa, H.; Tou, H.; Ishii, H.; Kudo, K.;
Nohara, M.; Harima, H. Pressure-induced superconductivity in
mineral calaverite AuTe2. J. Phys. Soc. Jpn. 2013, 82, 113704.
(15) Katayama, N.; Kudo, K.; Onari, S.; Mizukami, T.; Sugawara, K.;
Sugiyama, Y.; Kitahama; Iba, Y. K.; Fujimura, K.; Nishimoto, N.;
Nohara, M.; Sawa, H. Superconductivity in Ca1‑xLaxFeAs2: a novel
112-type iron pnictide with arsenic zigzag bonds. J. Phys. Soc. Jpn.
2013, 82, 123702.
(16) Yakita, H.; Ogino, H.; Okada, T.; Yamamoto, A.; Kishio, K.;
Tohei, T.; Ikuhara, Y.; Gotoh, Y.; Fujihisa, H.; Kataoka, K.; Eisaki, H.;
Shimoyama, J. A new layered iron arsenide superconductor:
(Ca,Pr)FeAs2. J. Am. Chem. Soc. 2014, 136, 846.
(17) Ni, N.; Allred, J. M.; Chan, B. C.; Cava, R. J. High Tc electron
doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5 super-
conductors with skutterudite intermediary layers. Proc. Natl. Acad.
Sci. U. S. A. 2011, 108, E1019−E1026.
̈
̈
(18) Lohnert, C.; Sturzer, T.; Tegel, M.; Frankovsky, R.; Friederichs,
G.; Johrendt, D. Superconductivity up to 35 K in the iron platinum
arsenides (CaFe1−xPtxAs)10Pt4−yAs8 with layered structures. Angew.
Chem., Int. Ed. 2011, 50, 9195.
(19) Chen, X.; Guo, J. G.; Gong, C. S.; Cheng, E. J.; Le, C. C.; Liu,
N.; Ying, T. P.; Zhang, Q. H.; Hu, J. P.; Li, S. Y.; Chen, X. L. c-Axis
dimer inducing dome-like superconductivity in weakly correlated
RE2Cu5As3O2 (RE = La, Pr). arXiv:1808.06857.
(20) Rodríguez-Carvajal, J. Abstract of the satellite meeting on
powder diffraction of the XV congress of the IUCr, Toulouse, France,
1990.
̈
(21) Dronskowski, R.; Blochl, P. E. Crystal orbital Hamilton
populations (COHP): energy-resolved visualization of chemical
bonding in solids based on density-functional calculations. J. Phys.
Chem. 1993, 97, 8617−8624.
́
(22) Maintz, S.; Deringer, V. L.; Tchougreeff, A. L.; Dronskowski, R.
LOBSTER: A tool to extract chemical bonding from plane-wave
based DFT. J. Comput. Chem. 2016, 37, 1030−1035.
(23) Dai, P. C.; Hu, J. P.; Dagotto, E. Magnetism and its microscopic
origin in iron-based high-temperature superconductors. Nat. Phys.
2012, 8, 709.
(24) Li, Y. K.; Luo, Y. K.; Li, L.; Chen, B.; Xu, X. F.; Dai, J. H.; Yang,
X. J.; Zhang, Li.; Cao, G. H.; Xu, Z. A. Kramers non-magnetic
superconductivity in LnNiAsO superconductors. J. Phys.: Condens.
Matter 2014, 26, 425701.
(25) Qiu, Y.; Bao, W.; Huang, Q.; Yildirim, T.; Simmons, J. M.;
Green, M. A.; Lynn, J. W.; Gasparovic, Y. C.; Li, J.; Wu, T.; Wu, G.;
Chen, X. H. Crystal structure and antiferromagnetic order in
NdFeAsO1−xFx (x = 0.0 and 0.2) superconducting compounds from
neutron diffraction measurements. Phys. Rev. Lett. 2008, 101, 257002.
G
DOI: 10.1021/acs.inorgchem.8b03360
Inorg. Chem. XXXX, XXX, XXX−XXX