Francesco Rocca

Istituto di Fotonica e Nanotecnologie

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Istituto di Fotonica e Nanotecnologie

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Francesco Rocca has a total of 222 co-authors. Here are the top co-authors by number of shared publications:

Paolo Fornasini
University of Trento
73 shared publications
G. Dalba
63 shared publications
Alexei Kuzmin
Institute of Solid State Physics University of Latvia Riga Latvia
28 shared publications
R. Grisenti
Dipartimento di Fisica, Università di Trento, I-38123 Povo (Trento), Italy
28 shared publications
Juris Purans
Institute of Solid State Physics, University of Latvia, 8 Kengaraga Str., LV1063 Riga, Latvia
23 shared publications
G Dalba
Department of Physics, University of Trento, 38123 Povo (Trento) Italy
20 shared publications

Latest Publications

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Cited by 17
- 1 September 2016
- Published by Elsevier in Journal of Alloys and Compounds
Local structure and magnetization of ferromagnetic Cu-doped ZnO films: No magnetism at the dopant?
by P.S. Vachhani, O. Šipr, A.K. Bhatnagar, R.K. Ramamoorthy, R.J. Choudhary, D.M. Phase, G. Dalba, A. Kuzmin, F. Rocca
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- 1 September 2016
- Published by Elsevier in Journal of Alloys and Compounds
Local structure and magnetization of ferromagnetic Cu-doped ZnO films: No magnetism at the dopant?
by P.S. Vachhani, O. Šipr, A.K. Bhatnagar, R.K. Ramamoorthy, R.J. Choudhary, D.M. Phase, G. Dalba, A. Kuzmin, F. Rocca
Cited by 17
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Cited by 29
- 2 June 2016
- Published by American Physical Society (APS) in Physical Review B
Interpretation of unexpected behavior of infrared absorption spectra of ${ScF}_{3}$ beyond the quasiharmonic approximation
by Sergei Piskunov, Pjotrs A. Žguns, Dmitry Bocharov, Alexei Kuzmin, Juris Purans, Aleksandr Kalinko, Robert A. Evarestov, Shehab E. Ali, Francesco Rocca
Scandium fluoride ( ${ScF}_{3}$ ), having cubic ${ReO}_{3}$ -type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we use the results of diffraction and extended x-ray absorption fine-structure (EXAFS) spectroscopy to interpret the influence of NTE on the temperature dependence of infrared absorption spectra of ${ScF}_{3}$ . Original infrared absorption and EXAFS experiments in a large temperature range are presented and interpreted using ab initio lattice dynamics simulations within and beyond quasiharmonic approximations. We demonstrate that ab initio electronic structure calculations, based on the linear combination of atomic orbitals method with hybrid functionals, are able to reproduce well the experimental values of lattice parameter $a_{0}$ , band gap $E_{g}$ , and lattice dynamics in ${ScF}_{3}$ . However, the simulations performed within quasiharmonic approximation fail to reproduce the temperature dependence of two infrared active bands due to the F–Sc–F bending (at 220 ${cm}^{- 1}$ ) and Sc–F stretching (at 520 ${cm}^{- 1}$ ) modes present in the infrared absorption spectra. To overcome this problem, an approach beyond the quasiharmonic approximation is proposed: It accounts for the negative thermal expansion of the lattice and for fluorine atom displacements due to strong F vibrational motion perpendicular to the cubic axes and allows us to explain qualitatively the temperature behavior of infrared spectra of ${ScF}_{3}$ .
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- 2 June 2016
- Published by American Physical Society (APS) in Physical Review B
Interpretation of unexpected behavior of infrared absorption spectra of ${ScF}_{3}$ beyond the quasiharmonic approximation
by Sergei Piskunov, Pjotrs A. Žguns, Dmitry Bocharov, Alexei Kuzmin, Juris Purans, Aleksandr Kalinko, Robert A. Evarestov, Shehab E. Ali, Francesco Rocca
Scandium fluoride ( ${ScF}_{3}$ ), having cubic ${ReO}_{3}$ -type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we use the results of diffraction and extended x-ray absorption fine-structure (EXAFS) spectroscopy to interpret the influence of NTE on the temperature dependence of infrared absorption spectra of ${ScF}_{3}$ . Original infrared absorption and EXAFS experiments in a large temperature range are presented and interpreted using ab initio lattice dynamics simulations within and beyond quasiharmonic approximations. We demonstrate that ab initio electronic structure calculations, based on the linear combination of atomic orbitals method with hybrid functionals, are able to reproduce well the experimental values of lattice parameter $a_{0}$ , band gap $E_{g}$ , and lattice dynamics in ${ScF}_{3}$ . However, the simulations performed within quasiharmonic approximation fail to reproduce the temperature dependence of two infrared active bands due to the F–Sc–F bending (at 220 ${cm}^{- 1}$ ) and Sc–F stretching (at 520 ${cm}^{- 1}$ ) modes present in the infrared absorption spectra. To overcome this problem, an approach beyond the quasiharmonic approximation is proposed: It accounts for the negative thermal expansion of the lattice and for fluorine atom displacements due to strong F vibrational motion perpendicular to the cubic axes and allows us to explain qualitatively the temperature behavior of infrared spectra of ${ScF}_{3}$ .
Cited by 29
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Cited by 8
- 1 May 2016
- Published by IOP Publishing in Journal of Physics: Conference Series
Ab initio molecular dynamics simulations of the Sc K-edge EXAFS of scandium trifluoride
by Dmitry Bocharov, Matthias Krack, Aleksandr Kalinko, Juris Purans, Francesco Rocca, Shehab E. Ali, Alexei Kuzmin
Ab initio molecular dynamics simulations of the Sc K-edge EXAFS of scandium trifluoride View the table of contents for this issue, or go to the journal homepage for more 2016 J. Phys.: Conf. Ser. 712 012009
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- 1 May 2016
- Published by IOP Publishing in Journal of Physics: Conference Series
Open Access
Ab initio molecular dynamics simulations of the Sc K-edge EXAFS of scandium trifluoride
by Dmitry Bocharov, Matthias Krack, Aleksandr Kalinko, Juris Purans, Francesco Rocca, Shehab E. Ali, Alexei Kuzmin
Ab initio molecular dynamics simulations of the Sc K-edge EXAFS of scandium trifluoride View the table of contents for this issue, or go to the journal homepage for more 2016 J. Phys.: Conf. Ser. 712 012009
Cited by 8
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Cited by 8
- 1 May 2016
- Published by IOP Publishing in Journal of Physics: Conference Series
Local structure of perovskites ReO₃and ScF₃with negative thermal expansion: interpretation beyond the quasiharmonic approximation
by Juris Purans, Sergei Piskunov, Dmitry Bocharov, Aleksandr Kalinko, Alexei Kuzmin, Shehab E. Ali, Francesco Rocca
We propose an approach beyond the quasiharmonic approximation for interpretation of EXAFS and XRD data and for ab initio calculations of electronic and vibration properties of materials with negative thermal expansion. Ab initio electronic structure and lattice dynamics calculations for cubic and distorted ScF3 were performed using the linear combination of atomic orbitals (LCAO) method. The band gap obtained in calculations for ScF3 is equal to 10.54 eV and agree well with the expected value. The calculated infrared spectra of F displaced (FD) cubic ScF3 allow us to predict that its mean Sc-F-Sc angle within NTE deviates from 180 degree.
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- 1 May 2016
- Published by IOP Publishing in Journal of Physics: Conference Series
Open Access
Local structure of perovskites ReO₃and ScF₃with negative thermal expansion: interpretation beyond the quasiharmonic approximation
by Juris Purans, Sergei Piskunov, Dmitry Bocharov, Aleksandr Kalinko, Alexei Kuzmin, Shehab E. Ali, Francesco Rocca
We propose an approach beyond the quasiharmonic approximation for interpretation of EXAFS and XRD data and for ab initio calculations of electronic and vibration properties of materials with negative thermal expansion. Ab initio electronic structure and lattice dynamics calculations for cubic and distorted ScF3 were performed using the linear combination of atomic orbitals (LCAO) method. The band gap obtained in calculations for ScF3 is equal to 10.54 eV and agree well with the expected value. The calculated infrared spectra of F displaced (FD) cubic ScF3 allow us to predict that its mean Sc-F-Sc angle within NTE deviates from 180 degree.
Cited by 8
Open Access
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Cited by 4
- 1 May 2016
- Published by IOP Publishing in Journal of Physics: Conference Series
Local dynamics and phase transition in quantum paraelectric SrTiO₃studied by TiK-edge x-ray absorption spectroscopy
by Andris Anspoks, Janis Timoshenko, Juris Purans, Francesco Rocca, Vladimir Trepakov, Alexander Dejneka, Mitsuru Itoh
Strontium titanate is a model quantum paraelectric in which, in the region of dominating quantum statistics, the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero- point motion contribution. The enhancement of atomic masses by the substitution of ¹⁶ O with ¹⁸O decreases the zero-point atomic motion, and low-T ferroelectricity in SrTi¹⁸O₃ is realized. In this study we report on the local structure of Ti in SrTi¹⁶O₃ and SrTi¹⁸O₃ investigated by Extended X-ray Absorption Fine Structure measurements in the temperature range 6 - 300 K.
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- 1 May 2016
- Published by IOP Publishing in Journal of Physics: Conference Series
Open Access
Local dynamics and phase transition in quantum paraelectric SrTiO₃studied by TiK-edge x-ray absorption spectroscopy
by Andris Anspoks, Janis Timoshenko, Juris Purans, Francesco Rocca, Vladimir Trepakov, Alexander Dejneka, Mitsuru Itoh
Strontium titanate is a model quantum paraelectric in which, in the region of dominating quantum statistics, the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero- point motion contribution. The enhancement of atomic masses by the substitution of ¹⁶ O with ¹⁸O decreases the zero-point atomic motion, and low-T ferroelectricity in SrTi¹⁸O₃ is realized. In this study we report on the local structure of Ti in SrTi¹⁶O₃ and SrTi¹⁸O₃ investigated by Extended X-ray Absorption Fine Structure measurements in the temperature range 6 - 300 K.
Cited by 4
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Cited by 1
- 18 September 2015
- Published by Wiley
Xafs Spectroscopy and Glass Structure
by Giuseppe Dalba, Francesco Rocca
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- 18 September 2015
- Published by Wiley
Xafs Spectroscopy and Glass Structure
by Giuseppe Dalba, Francesco Rocca
Cited by 1
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Cited by 4
- 26 August 2015
- Published by Taylor & Francis in Ferroelectrics
Local Structure Studies of Ti for SrTi¹⁶O₃and SrTi¹⁸O₃by Advanced X-ray Absorption Spectroscopy Data Analysis
by A. Anspoks, J. Timoshenko, D. Bocharov, J. Purans, F. Rocca, A. Sarakovskis, V. Trepakov, A. Dejneka, M. Itoh
Strontium titanate is a model quantum paraelectric in which in the region of dominating quantum statistics the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero-point motion contribution. The enhancement of atomic masses by the substitution of ¹⁸O for ¹⁶O decreases the zero-point atomic motion and low-T ferroelectricity in SrTi¹⁸O₃ is realized. In this study we report on the local structure of Ti in SrTi¹⁶O₃ and SrTi¹⁸O₃ by Ti K-edge extended x-ray absorption fine structure measurements in temperature range 6 – 300 K.
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- 26 August 2015
- Published by Taylor & Francis in Ferroelectrics
Local Structure Studies of Ti for SrTi¹⁶O₃and SrTi¹⁸O₃by Advanced X-ray Absorption Spectroscopy Data Analysis
by A. Anspoks, J. Timoshenko, D. Bocharov, J. Purans, F. Rocca, A. Sarakovskis, V. Trepakov, A. Dejneka, M. Itoh
Strontium titanate is a model quantum paraelectric in which in the region of dominating quantum statistics the ferroelectric instability is inhibited due to nearly complete compensation of the harmonic contribution into ferroelectric soft mode frequency by the zero-point motion contribution. The enhancement of atomic masses by the substitution of ¹⁸O for ¹⁶O decreases the zero-point atomic motion and low-T ferroelectricity in SrTi¹⁸O₃ is realized. In this study we report on the local structure of Ti in SrTi¹⁶O₃ and SrTi¹⁸O₃ by Ti K-edge extended x-ray absorption fine structure measurements in temperature range 6 – 300 K.
Cited by 4
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Cited by 15
- 16 July 2015
- Published by American Physical Society (APS) in Physical Review B
X-ray absorption spectroscopy study of local dynamics and thermal expansion in ${ReO}_{3}$
by J. Purans, P. Fornasini, S. E. Ali, G. Dalba, A. Kuzmin, F. Rocca
The thermal expansion of polycrystalline ${ReO}_{3}$ is studied in vacuum by x-ray diffraction from 300 to 600 K and by extended x-ray absorption fine structure (EXAFS) at the Re $L_{3}$ edge from 30 to 600 K. A detailed EXAFS analysis is presented up to the sixth coordination shell around Re. The crystal thermal expansion is weak throughout the explored range, negative below 100 K, positive from 150 to 500 K, and negative again above 500 K. The analysis of mean square relative displacements obtained by EXAFS and of mean square displacements available from x-ray and neutron diffraction measurements confirms the presence of significant static disorder in the investigated samples. EXAFS results suggest that below 500 K in ${ReO}_{3}$ at least some of the octahedra are slightly and disorderly rotated by an average angle $〈 θ 〉$ , whose value decreases when the temperature increases. This explains why ${ReO}_{3}$ , in spite of the possibility of supporting rigid unit modes, shows a weak positive expansion at increasing temperatures, from 150 up to 500 K. Results are discussed and compared with recent experimental and theoretical work on materials characterized by negative thermal expansion.
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- 16 July 2015
- Published by American Physical Society (APS) in Physical Review B
X-ray absorption spectroscopy study of local dynamics and thermal expansion in ${ReO}_{3}$
by J. Purans, P. Fornasini, S. E. Ali, G. Dalba, A. Kuzmin, F. Rocca
The thermal expansion of polycrystalline ${ReO}_{3}$ is studied in vacuum by x-ray diffraction from 300 to 600 K and by extended x-ray absorption fine structure (EXAFS) at the Re $L_{3}$ edge from 30 to 600 K. A detailed EXAFS analysis is presented up to the sixth coordination shell around Re. The crystal thermal expansion is weak throughout the explored range, negative below 100 K, positive from 150 to 500 K, and negative again above 500 K. The analysis of mean square relative displacements obtained by EXAFS and of mean square displacements available from x-ray and neutron diffraction measurements confirms the presence of significant static disorder in the investigated samples. EXAFS results suggest that below 500 K in ${ReO}_{3}$ at least some of the octahedra are slightly and disorderly rotated by an average angle $〈 θ 〉$ , whose value decreases when the temperature increases. This explains why ${ReO}_{3}$ , in spite of the possibility of supporting rigid unit modes, shows a weak positive expansion at increasing temperatures, from 150 up to 500 K. Results are discussed and compared with recent experimental and theoretical work on materials characterized by negative thermal expansion.
Cited by 15
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- 1 October 2014
- Published by Elsevier in Journal of Non-Crystalline Solids
The 12th International Conference on the Structure of Non-Crystalline Materials (NCM12), Riva del Garda-Trento, Italy July 7–13, 2013
by Giuseppe Dalba, Francesco Rocca
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- 1 October 2014
- Published by Elsevier in Journal of Non-Crystalline Solids
The 12th International Conference on the Structure of Non-Crystalline Materials (NCM12), Riva del Garda-Trento, Italy July 7–13, 2013
by Giuseppe Dalba, Francesco Rocca
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Cited by 11
- 1 October 2014
- Published by Elsevier in Journal of Non-Crystalline Solids
Ionic conductivity, electric modulus and mechanical relaxations in silver iodide–silver molybdate glasses
by Andrea Mandanici, Anna Raimondo, Mauro Federico, Maria Cutroni, Piercarlo Mustarelli, Cristina Armellini, Francesco Rocca
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- 1 October 2014
- Published by Elsevier in Journal of Non-Crystalline Solids
Ionic conductivity, electric modulus and mechanical relaxations in silver iodide–silver molybdate glasses
by Andrea Mandanici, Anna Raimondo, Mauro Federico, Maria Cutroni, Piercarlo Mustarelli, Cristina Armellini, Francesco Rocca
Cited by 11

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