<i>PSEUDO</i>: a program for a pseudosymmetry search

Kroumova, E.; Aroyo, M. I.; Pérez-Mato, J. M.; Ivantchev, S.; Igartua, J. M.; Wondratschek, H.

doi:10.1107/s0021889801011852

Cited by 66 publications

(48 citation statements)

References 2 publications

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“…We made use of the VASP2WANNIER90 interface to interpolate the band structures to a finer grid 53,54 . The search of the centric structure, as well as the symmetry analysis, was performed using the PSEUDO and AMPLIMODES tools on the Bilbao Crystallographic Server 55,56 . Figures are plotted using the VESTA package 57 .…”

Section: Methodsmentioning

confidence: 99%

Tunable ferroelectric polarization and its interplay with spin–orbit coupling in tin iodide perovskites

et al. 2014

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Ferroelectricity is a potentially crucial issue in halide perovskites, breakthrough materials in photovoltaic research. Using density functional theory simulations and symmetry analysis, we show that the lead-free perovskite iodide (FA)SnI 3 , containing the planar formamidinium cation FA, (NH 2 CHNH 2 ) þ , is ferroelectric. In fact, the perpendicular arrangement of FA planes, leading to a 'weak' polarization, is energetically more stable than parallel arrangements of FA planes, being either antiferroelectric or 'strong' ferroelectric. Moreover, we show that the 'weak' and 'strong' ferroelectric states with the polar axis along different crystallographic directions are energetically competing. Therefore, at least at low temperatures, an electric field could stabilize different states with the polarization rotated by p/4, resulting in a highly tunable ferroelectricity appealing for multistate logic. Intriguingly, the relatively strong spin-orbit coupling in noncentrosymmetric (FA)SnI 3 gives rise to a co-existence of Rashba and Dresselhaus effects and to a spin texture that can be induced, tuned and switched by an electric field controlling the ferroelectric state.

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Section: Methodsmentioning

confidence: 99%

Tunable ferroelectric polarization and its interplay with spin–orbit coupling in tin iodide perovskites

et al. 2014

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“…The smaller this distance, the higher the pseudosymmetry. If all the distances between the original and virtual atomic positions in the supergroup are smaller than a tolerance value (in the following Δ # 2 Å, [39,42]), the structure is said to be pseudosymmetric with respect to the supergroup G.…”

Section: Analysis Of Pseudosymmetrymentioning

confidence: 99%

Twinning and pseudosymmetry under high pressure

Friese

Grzechnik

2014

Zeitschrift Für Kristallographie – Crystalline Materials

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Abstract:We review the available information on crystal twinning at high pressures and analyze the effect of hydrostatic pressure on the pseudosymmetry of selected compounds. Twinning by merohedry, type I and II, as well as pseuomerohedral twinning at high pressures has been described. For twinning by merohedry type I (inversion twinning) a reliable characterization of the twin domains and volume fractions is difficult and largely depends on the experimental conditions, i.e. the number of measured Friedel pairs and the chosen wavelength. For twinning by merohedry, type II, and for twinning by pseuodmerohedry twin volume fractions could be reliably determined for several cases. In none of these a significant influence of hydrostatic pressure on the volume fractions of the individuals was observed. Pressure-induced twinning has been observed for compounds which undergo first-order phase transitions. The twinning operation in the described cases is related to the loss of rotational symmetry elements of the higher symmetrical polymorph although the high and low pressure phases are not in group-subgroup relationship. The analysis of pseudosymmetry of several compounds as a function of pressure suggests that this parameter can be used to predict the (in)stability of compounds. In particular, a decrease in pseudosymmetry seems to be strongly correlated with the occurrence of first-order phase transitions in which the crystal breaks or amorphizes. The effect of hydrostatic and chemical pressure on the pseudosymmetry of the crystal structures can lead to different or even opposite trends, suggesting that the increase or decrease of pseudosymmetry cannot be understood as a pure volume effect.

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“…This idealized prototype structure can be found using the pseudosymmetry searching software PSEUDO. [44] Basically, the structure is the ideal perovskite except for the ordering of the cations and there is no BO 6 and B ′ O 6 octahedral tilting or rotation. Using the symmetry mode analysis program AMPLIMODES [45], one can decompose the distortion relating the relaxed monoclinic structure with this prototypical structure into symmetryadapted distortion modes.…”

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confidence: 99%

Large ferroelectric polarization in the new double perovskite NaLaMnWO6 induced by non-polar instabilities

Fukushima

Stroppa

Picozzi

et al. 2011

Phys. Chem. Chem. Phys.

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103

127

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Based on density functional theory calculations and group theoretical analysis, we have studied NaLaMnWO6 compound which has been recently synthesized [Phys. Rev. B 79, 224428 (2009)] and belongs to the AA ′ BB ′ O6 family of double perovskites. At low temperature, the structure has monoclinic P 21 symmetry, with layered ordering of the Na and La ions and rocksalt ordering of Mn and W ions. The Mn atoms show an antiferromagnetic (AFM) collinear spin ordering, and the compound has been reported as a potential multiferroic. By comparing the low symmetry structure with a parent phase of P 4/nmm symmetry, two distortion modes are found dominant. They correspond to MnO6 and WO6 octahedron tilt modes, often found in many simple perovskites. While in the latter these common tilting instabilities yield non-polar phases, in NaLaMnWO6 the additional presence of the A-A ′ cation ordering is sufficient to make these rigid unit modes as a source of the ferroelectricity. Through a trilinear coupling with the two unstable tilting modes, a significant polar distortion is induced, although the system has no intrinsic polar instability. The calculated electric polarization resulting from this polar distortion is as large as ∼ 16 µC/cm 2 . Despite its secondary character, this polarization is coupled with the dominant tilting modes and its switching is bound to produce the switching of one of two tilts, enhancing in this way a possible interaction with the magnetic ordering. The transformation of common non-polar purely steric instabilities into sources of ferroelectricity through a controlled modification of the parent structure, as done here by the cation ordering, is a phenomenon to be further explored.Perovskite oxides are one of the most interesting and studied classes of inorganic compounds. They show many interesting properties such as ferroelectricity, ferromagnetism, superconductivity, colossal magnetoresistance, etc.[1] The prototype structure is the simple ABO 3 , where the three-dimensional framework of corner-sharing BO 6 octahedra form 12-coordinate cavities occupied by the larger A cations. The possibility of A-or B-substitution gives rise to a large compositional range with different properties and symmetries. A well studied case is the 50:50 substitution of B-site in the double perovskites A 2 BB ′ O 6 , where the B and B ′ cations order in a rock-salt fashion.[2, 3] Analogously, ordering of the A-cations can also occur, showing a strong preference for a layered arrangement.[4-6] Finally, simultaneous Aand B-site cation ordering can also occur in compounds of type AA ′ BB ′ O 6 .[7] These compounds are interesting from a structural point of view since they exhibit rocksalt ordering of B-site cations and layered ordering of A-site cations. However, they are relatively unexplored, * Present address: Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan because this type of ordering is very rare. [7,8] Clearly, the presence of four different distinct cation sit...

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PSEUDO: a program for a pseudosymmetry search

Abstract: computer program abstractsThis category provides a rapid means of communicating up-to-date information concerning both new programs or systems and significant updates to existing ones. Submissions should follow the standard format given in

Cited by 66 publications

References 2 publications

Tunable ferroelectric polarization and its interplay with spin–orbit coupling in tin iodide perovskites

Tunable ferroelectric polarization and its interplay with spin–orbit coupling in tin iodide perovskites

Twinning and pseudosymmetry under high pressure

Large ferroelectric polarization in the new double perovskite NaLaMnWO6 induced by non-polar instabilities

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