focused issues

IUCr Journals regularly produce focused special issues on topics of key interest to readers.

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Forthcoming focused issues

Quantum Crystallography

Guest editors: Paulina Dominiak, Angel Martín Pendás and Krzysztof Wozniak

The progress of civilization and technology is based on the development of science, which depends on the quality of data and the methods used to transform them into scientific laws or to validate newly proposed theories.

In 2025 we will celebrate the centenary of Erwin Schrödinger's development of wave mechanics and Werner Heisenberg's, Max Born's and Pascual Jordan's proposal of matrix mechanics. This was the beginning of the era of quantum mechanics, whose history is inextricably intertwined with the growth of Crystallography since the first X-ray diffraction experiments on crystals were carried out.

The successful marriage of modern crystallography and quantum mechanics is based on the fact that the former requires quantum-mechanical models to refine crystal structures, while the latter very often demands crystal structures as a starting point for the extensive quantum-mechanical analyses needed to understand and predict the properties of the advanced materials on which our civilization depends.

It is not surprising, therefore, that Quantum Crystallography (QCr), situated at the intersection of Quantum Mechanics and Crystallography, is a burgeoning field that promises to bridge the gap between theory and experiment in understanding the fundamental behavior of matter at the atomic and molecular level.

It is an incomprehensible paradox that more than a century after the introduction of the first scattering model in crystallography, the independent atom model (IAM), more than 99% of all crystal structures (about 2 million) are still refined using it. To the major investments in improving the quality of the measured data, we contrast the scarce resources employed to improve the methods used to interpret them. In a sense, the overwhelming success of the IAM has slowed the development and application of new methodologies, new models of atomic electron densities, in refining structures. These new methodologies beyond the IAM, being actively developed in QCr, allow the determination of accurate and precise electron density (charge and spin) distributions in position and momentum space from diffraction and scattering experiments, and also provide a wealth of parameters used to characterize the nature of chemical bonding or to quantify physicochemical properties.

The current development of Quantum Crystallography goes far beyond the original definition given by Massa, Karle and Huang (Int. J. Quantum Chem. 1999, 73, 439). According to this, the measured intensities of reflections can be used to extract directly the wavefunctions or density matrices of a system and quantum-mechanical calculations can also be used to enhance the accuracy of the crystallographic refinement. However, as is the case in the evolution of most scientific disciplines, this traditional statement does not embrace many newly proposed applications of QCr, and other definitions are circulating both in the scientific literature and at various scientific conferences. It is thus time to show these new advances.

In this virtual issue, we would like to show the dynamic development of QCr, its thematic richness, and possible relations with some complementary fields. We hope that this will enable the identification of the main directions in which the quantum-crystallographic scientific revolution is evolving. Looking back, it is difficult to understand why it is only now that quantum crystallography is developing so intensively. We have no doubt that the potential of quantum crystallography is enormous and will change the face of many fields of contemporary and future science.

The fields that are expected to benefit from the development of QCr are summarized below:

1. Determination of complex molecular structures: By coupling quantum-mechanical calculations to experimental techniques, QCr enables researchers to overcome traditional barriers in both fields, for example by providing accurate hydrogen-atom positions from conventional X-ray diffraction patterns with similar precision to that obtained by neutron diffraction. Proofs of concept or simply proposals related to overcoming these kinds of limits are welcome.

2. Materials science: Understanding the microscopic structure of materials is paramount to developing new materials with tailored properties. Since the output of QCr is not just structural determination, but a wealth of electronic and bonding information, we expect it to provide new insights that will facilitate the design of materials for a variety of applications, from pharmaceuticals to electronics. Examples or proposals are welcome.

3. Drug discovery: In pharmaceutical research, knowledge of the energy landscape associated with structural determination is essential for rational drug design. QCr techniques are capable of accurately revealing and quantifying the interactions underlying the crystal packing observed in the case of polymorphs, and promise to be very useful in revealing the nature of drug-receptor interactions, guiding the development of more effective and targeted therapies. Examples or proposals in this direction are also welcome.

4. Theoretical and computational chemistry: Quantum crystallography synergizes with theoretical chemistry, providing experimental validation for computational models and methodologies. This interdisciplinary collaboration improves the accuracy and predictive power of computational chemistry approaches. Subdisciplines of QCr such as the X-ray restrained wavefunction method (XRW) promise to help theoreticians propose better density-functional approximations or examine scars in wavefunctions, or electron densities, of strong correlations that currently escape theoretical manipulation. Applications or proposals that are well known in theory but not in experiment, or vice versa, and that could thus benefit from the QCr interplay between both fields are also expected.

5. Machine learning: QCr should take advantage of the opportunities offered by ML. Just as in the recent past the use of large databases was parallel to the development of the incipient QCr discipline, it is expected that the integration of ML in Crystallography will affect all its steps, from data reduction to model validation. Proposals or examples of the use of machine-learning methods already existing in the QCr ecosystem are also expected, as well as new methods that can use computational or experimental data (or both) to train ML algorithms.




A selection of focused issues published since 1998 is given below.

Special issues

Machine learning in crystallography and structural science
Acta Cryst. Machine learning in crystallography and structural science (26 January 2024)

Artificial neural networks
J. Appl. Cryst. Artificial neural networks: applications in X-ray photon science and crystallography (10 January 2024)

Tools for teaching crystallography
Acta Cryst. Modern approaches and tools for teaching crystallography

Magnetic small-angle neutron scattering
J. Appl. Cryst. Magnetic small-angle neutron scattering – from nanoscale magnetism to long-range magnetic structures (1 February 2023)

SAS2022
J. Appl. Cryst. Small-angle scattering special issue (1 December 2023)

Halogen, chalcogen, pnictogen and tetrel bonds
Acta Cryst. Halogen, chalcogen, pnictogen and tetrel bonds: structural chemistry and beyond (May 2023)

Current trends in macromolecular model refinement and validation
Acta Cryst. CCP4 Study Weekend 2023 - Current trends in macromolecular model refinement and validation

Jerry P. Jasinski tribute
Acta Cryst. Jerry P. Jasinski tribute

Actinide Physics and Chemistry
J. Synchrotron Rad. Actinide Physics and Chemistry with Synchrotron Radiation (22 September 2022)

Integrating Structural Biology
Acta Cryst. CCP4 Study Weekend 2023 - Integrating Structural Biology

Room temperature biological crystallography
Acta Cryst. Room temperature biological crystallography

Special issue on structure correlation and dynamics in crystals: a tribute to Professor Hans-Beat Bürgi
Acta Cryst. Volume B78, Part 3 Number 1 (pp. 281-424, 1 June 2022)

Quantum crystallography
Acta Cryst. Quantum crystallography special issue (December 2021)

Ptychography: software and technical developments
J. Appl. Cryst. Ptychography: software and technical developments special issue (1 April 2021)

Research reported at the 25th IUCr Congress
Acta Cryst. IUCr 2021

X-ray Radiation Damage to Biological Samples
J. Synchrotron Rad. Volume 28, Part 5 (pp. 1273-1671, 1 September 2021)

X-ray Free-Electron Lasers
J. Synchrotron Rad. X-ray Free-Electron Lasers (6 May 2020)

Model building, validation and representation in MX and cryoEM
Acta Cryst. CCP4 Study Weekend 2020 - Model building, validation and representation in MX and cryoEM

CCP-EM
Acta Cryst. CCP-EM Spring Symposium 2019

Molecular replacement
Acta Cryst. CCP4 Study Weekend 2019 - Molecular replacement

PhotonDiag2018
J. Synchrotron Rad. PhotonDiag2018 (23 April 2020)

X-ray Radiation Damage to Biological Samples
J. Synchrotron Rad. Volume 26, Part 4 (pp. 907-1399, 1 July 2019)

CCP4 - Multi and serial data collection and processing
Acta Cryst. Volume D75, Part 2 (pp. 111-241, 1 February 2019)

State-of-the-art cryo-electron microscopy
Acta Cryst. Volume F75, Part 1 (pp. 1-72, 1 January 2019)

Aperiodic 2018
Acta Cryst. Aperiodic 2018 (15 March 2019)

Neutron scattering for the study of biological systems
Acta Cryst. Volume D74, Part 12 (pp. 1126-1244, 1 December 2018)

Special issue on mineralogical crystallography
Acta Cryst. Volume B74, Part 6 (pp. 467-744, 1 December 2018)

Special issue on Polyoxometalates
Acta Cryst. Volume C74, Part 11 (pp. 1180-1560, 1 November 2018)

5th International Symposium on Diffraction Structural Biology (ISDSB2016)
Acta Cryst. Volume D74, Part 8 (pp. 713-813, 1 August 2018)

Crystallography of glycoproteins and protein-carbohydrate complexes
Acta Cryst. Volume F74, Part 8 (pp. 441-523, 1 August 2018)

Q2XAFS2017 Workshop papers
J. Synchrotron Rad. Volume 25, Part 4 (pp. 918-1276, 1 July 2018)

Advanced neutron scattering instrumentation
J. Appl. Cryst. Advanced neutron scattering instrumentation special issue (1 June 2018)

Weak interactions in crystals: an integrated approach
Acta Cryst. Volume E74, Part 5 (pp. 569-765; 1 May 2018)

CCP4 - From crystal to structure with CCP4 (Part 2)
Acta Cryst. Volume D74, Part 3 (pp. 167-244, 1 March 2018)

CCP4 - From crystal to structure with CCP4 (Part 1)
Acta Cryst. Volume D74, Part 2 (pp. 67-166, 1 February 2018)

PhotonDiag2017 Workshop papers
J. Synchrotron Rad. Volume 25, Part 1 (pp. 1-303, 1 January 2018)

Special issue on charge density, photocrystallography and time-resolved crystallography: a tribute to Professor Philip Coppens
Acta Cryst. Volume B73, Part 4 (pp. 519-774, 1 August 2017)

Proceedings of the CCP-EM Spring Symposium 2016
Acta Cryst. Volume D73, Part 6 (pp. 467-548, 1 June 2017)

13th Biennial Conference on High-Resolution X-ray Diffraction and Imaging (XTOP2016)
J. Appl. Cryst. High-resolution X-ray diffraction and imaging special issue (1 June 2017)

Special issue on halogen bonding
Acta Cryst. Volume B73, Part 2 (pp. 135-323, 1 April 2017)

CCP4 - Protein-ligand complexes: understanding biological chemistry (Part 2)
Acta Cryst. Volume D73, Part 3 (pp. 195-285, 1 March 2017)

Special issue on NMR Crystallography
Acta Cryst. Volume C73, Part 3 (pp. 126-304, 1 March 2017)

CCP4 - Protein-ligand complexes: understanding biological chemistry (Part 1)
Acta Cryst. Volume D73, Part 2 (pp. 77-194, 1 February 2017)

X-ray Radiation Damage to Biological Crystalline Samples
J. Synchrotron Rad. Volume 24, Part 1 (pp. 1-375, 1 January 2017)

Small-angle scattering special issue
J. Appl. Cryst. Small-angle scattering special issue (1 December 2016)

100 years of the Debye scattering equation
Acta Cryst. Volume A72, Part 6 (pp. 589-705, 1 November 2016)

Special issue on Scorpionates: a golden anniversary
Acta Cryst. Volume C72, Part 11 (pp. 766-922, 1 November 2016)

CCP-FEL: a collection of computer programs for FEL research
J. Appl. Cryst. CCP-FEL: a collection of computer programs for FEL research (1 August 2016)

Protein crystallization - state of the art
Acta Cryst. Protein crystallization - state of the art (2016)

Special issue on crystal structure prediction
Acta Cryst. Volume B72, Part 4 (pp. 435-657, 1 August 2016)

CCP4 - Advances in experimental phasing
Acta Cryst. Volume D72, Part 3 (pp. 291-453, 1 March 2016)

PhotonDiag2015 Workshop
J. Synchrotron Rad. Volume 23, Part 1 (pp. 1-382, 1 January 2016)

Special issue on energy materials
Acta Cryst. Volume B71, Part 6 (pp. 583-813, 1 December 2015)

ICCBM15 - selected articles
Acta Cryst. Volume F71, Part 7 (pp. 805-928, 1 July 2015)

12th Biennial Conference on High-Resolution X-ray Diffraction and Imaging (XTOP2014)
J. Appl. Cryst. X-ray diffraction and imaging special issue (27 June 2015)

Molecular parasitology - advances in biology and supporting drug discovery
Acta Cryst. Volume F71, Part 5 (pp. 483-621, 1 May 2015)

X-ray Free-Electron Lasers
J. Synchrotron Rad. Volume 22, Part 3 (pp. 471-866, 1 May 2015)

X-ray Radiation Damage to Biological Crystalline Samples
J. Synchrotron Rad. Volume 22, Part 2 (pp. 195-470, 1 March 2015)

CCP4 - Two Way Street - Complementary Methods
Acta Cryst. Volume D71, Part 1 (pp. 1-172, 1 January 2015)

Diffraction data deposition
Acta Cryst. Volume D70, Part 10 (pp. 2500-2780, 1 October 2014)

Diffraction-Limited Storage Rings and New Science Opportunities
J. Synchrotron Rad. Volume 21, Part 5 (pp. 837-1216, 1 September 2014)

Special issue on non-ambient crystallography
Acta Cryst. Volume B70, Part 3 (pp. 399-615, 1 June 2014)

Special issue on crystal engineering
Acta Cryst. Volume B70, Part 1 (pp. 1-195, 1 February 2014)

Small-Angle Scattering
J. Appl. Cryst. Small-angle scattering special issue (19 February 2014)

Mathematical crystallography
Acta Cryst. Mathematical crystallography (9 December 2014)

Coordination polymers
Acta Cryst. Virtual issue on Coordination polymers (1 July 2014)

X-ray Diffraction Microscopy
J. Appl. Cryst. X-ray diffraction microscopy special issue (15 March 2013)

Interplay of crystallography, spectroscopy and theoretical methods for solving chemical problems
Acta Cryst. Volume C69, Part 12 (pp. 1415-1566, 15 December 2013)

CCP4 Study Weekend: Molecular replacements, Nottingham, UK, January 2013
Acta Cryst. Volume D69, Part 11 (pp. 2165-2292, 1 November 2013)

Pharmaceuticals, drug discovery and natural products
Acta Cryst. Volume C69, Part 11 (pp. 1205-1414, 15 November 2013)

Special issue on Scorpionates
Acta Cryst. Volume C69, Part 9 (pp. 937-1084, 15 September 2013)

4th International Symposium on Diffraction Structural Biology, Nagoya, Japan, May 2013
J. Synchrotron Rad. Volume 20, Part 6 (pp. 819-1012, 1 November 2013)

11th Biennial Conference on High-Resolution X-ray Diffraction and Imaging (XTOP2012), St Petersburg, Russia, September 2012
J. Appl. Cryst. Volume 46, Part 4 (pp. 841-1248, 1 August 2013)

CCP4 Study Weekend: Data collection and processing, University of Warwick, UK, January 2012
Acta Cryst. Volume D69, Part 7 (pp. 1193-1332, 1 July 2013)

Integrated Software for Integrative Structural Biology
Acta Cryst. Volume D69, Part 5 (pp. 681-924, 1 May 2013)

Bragg Centennial - celebrating 100 years of X-ray crystallography
Acta Cryst. Volume A69, Part 1 (pp. 1-122, 1 January 2013)

Seventh International Workshop on X-ray Damage to Biological Crystalline Samples, Diamond Light Source, UK, March 2012
J. Synchrotron Rad. Volume 20, Part 1 (pp. 1-208, 1 January 2013)

Absolute structure
Acta Cryst. Virtual issue on Absolute structure (1 December 2012)

International Workshop on Improving Data Quality and Quantity for XAFS Experiments (Q2XAFS2011), Photon Factory, Tsukuba, Japan, December 2011
J. Synchrotron Rad. Volume 19, Part 6 (pp. 849-1066, 1 November 2012)

CCP4 Study Weekend: Model building, refinement and validation, University of Warwick, UK, January 2011
Acta Cryst. Volume D68, Part 4 (pp. 325-496, 1 April 2012)

Polymorphism
Acta Cryst. Virtual issue on Polymorphism (1 December 2011)

The Seattle Structural Genomics Center for Infectious Disease
Acta Cryst. Volume F67, Part 9 (pp. 979-1158, 1 September 2011)

Sixth International Workshop on X-ray Radiation Damage to Biological Crystalline Samples, Menlo Park, CA, USA, March 2010
J. Synchrotron Rad. Volume 18, Part 3 (pp. 313-537, 1 May 2011)

CCP4 Study Weekend: From Crystal to Structure with CCP4, Nottingham, UK, January 2010
Acta Cryst. Volume D67, Part 4 (pp. 233-394, 1 April 2011)

Third International Symposium on Diffraction Structural Biology (ISDSB2010), Orsay/Saint Aubin, France, 25-28 May 2010
J. Synchrotron Rad. Volume 18, Part 1 (pp. 1-99, 1 January 2011)

Neutrons in biology
Acta Cryst. Volume D66, Part 11 (pp. 1121-1268, 1 November 2010)

Crystallography education and training for the 21st century
J. Appl. Cryst. Volume 43, Part 5 Number 2 (pp. 1137-1284, 1 October 2010)

Joint Center for Structural Genomics (JCSG)
Acta Cryst. Volume F66, Part 10 (pp. 1137-1405, 1 October 2010)

CCP4 Study Weekend on Experimental Phasing and Radiation Damage, Nottingham, UK, January 2009
Acta Cryst. Volume D66, Part 4 (pp. 325-501, 1 April 2010)

Dynamical structural science
Acta Cryst. Volume A66, Part 2 (pp. 133-280, 1 March 2010)

Synchrotron radiation in soil and geosciences
J. Synchrotron Rad. Volume 17, Part 2 (pp. 147-298, 1 March 2010)

RIKEN-UK structural genomics
Acta Cryst. Volume F65, Part 12 (pp. 1200-1319, 1 December 2009)

Advances and synergy of high-pressure sciences at synchrotron sources
J. Synchrotron Rad. Volume 16, Part 6 (pp. 697-883, 1 November 2009)

Workshop on New Algorithms in Macromolecular Crystallography and Electron Microscopy, Leiden, The Netherlands, May 2008
Acta Cryst. Volume D65, Part 7 (pp. 623-732, 1 July 2009)

Fifth International Workshop on X-ray Damage to Biological Crystalline Samples, Villigen, Switzerland, March 2008
J. Synchrotron Rad. Volume 16, Part 2 (pp. 129-316, 1 March 2009)

CCP4 Study Weekend on Low-Resolution Structure Determination and Validation, Leeds, UK, January 2008
Acta Cryst. Volume D65, Part 2 (pp. 101-199, 1 February 2009)

Second International Symposium on Diffraction Structural Biology, ISDSB2007, Tower Hall Funabori, Tokyo, Japan, 10-13 September 2007
J. Synchrotron Rad. Volume 15, Part 3 (pp. 199-322, 1 May 2008)

CCP4 Study Weekend on Molecular Replacement, Reading, UK, January 2007
Acta Cryst. Volume D64, Part 1 (pp. 1-140, 1 January 2008)

13th International Conference on Small-Angle Scattering, Kyoto, Japan, 9-13 July 2006
J. Appl. Cryst. Volume 40, Part s1 (pp. s1-s705, 21 April 2007)

CCP4 Study Weekend on Crystallography of Complexes, Leeds, UK, January 2006
Acta Cryst. Volume D63, Part 1 (pp. 1-117, 1 January 2007)

Fourth International Workshop on X-ray Damage to Biological Crystalline Samples, Harima, Japan, March 2006
J. Synchrotron Rad. Volume 14, Part 1 (pp. 1-180, 1 January 2007)

Structural Proteomics IN Europe
Acta Cryst. Volume D62, Part 10 (pp. 1103-1285, 1 October 2006)

Get-Phases, Beijing, People's Republic of China, October-November 2005
Acta Cryst. Volume D62, Part 8 (pp. 843-945, 1 August 2006)

International School on Mathematical and Theoretical Crystallography, Nancy, France, June 2005
Acta Cryst. Volume A62, Part 2 (pp. 47-145, 1 March 2006)

Detectors
J. Synchrotron Rad. Volume 13, Part 2 (pp. 97-226, 1 March 2006)

CCP4 Study Weekend on Data Collection and Analysis, Reading, UK, January 2005
Acta Cryst. Volume D62, Part 1 (pp. 1-124, 1 January 2006)

10th International Conference on the Crystallization of Biological Macromolecules, Beijing, People's Republic of China, 5-8 June 2004
Acta Cryst. Volume D61, Part 6 (pp. 651-843, 1 June 2005)

CCP4 Study Weekend on Model Building and Refinement, Leeds, UK, January 2004
Acta Cryst. Volume D60, Part 12 Number 1 (pp. 2115-2294, 1 December 2004)

New Information from Modern Charge Density Methods, Third European Charge Density Meeting, Sandbjerg Estate, Denmark, 24-29 June 2003
Acta Cryst. Volume A60, Part 5 (pp. 357-516, 1 September 2004)

CCP4 Study Weekend on Experimental Phasing, York, UK, January 2003
Acta Cryst. Volume D59, Part 11 (pp. 1881-2050, 1 November 2003)

XIV Russian Synchrotron Radiation Conference, SR2002, Novosibirsk, Russia, 15-19 July 2002
J. Synchrotron Rad. Volume 10, Part 5 (pp. 343-407, 1 September 2003)

12th International Conference on Small-Angle Scattering, Venice, Italy, 25-29 August 2002
J. Appl. Cryst. Volume 36, Part 3 Number 1 (pp. 373-868, 1 June 2003)

BioXAS Study Weekend on Contribution of BioXAS to Structural Genomics: Developments in Theory and Refinement Methods, Orsay, France, 30 June-1 July 2001
J. Synchrotron Rad. Volume 10, Part 1 (pp. 1-112, 1 January 2003)

Second International Workshop on X-ray Damage to Crystalline Biological Samples, Chicago, USA, December 2001
J. Synchrotron Rad. Volume 9, Part 6 (pp. 327-413, 1 November 2002)

CCP4 Study Weekend on High-Throughput Structure Determination, York, UK, January 2002
Acta Cryst. Volume D58, Part 11 (pp. 1897-1970, 1 November 2002)

9th International Conference on the Crystallization of Biological Macromolecules, Jena, Germany, 23-28 March 2002
Acta Cryst. Volume D58, Part 10 Number 1 (pp. 1511-1764, 1 October 2002)

Special issue on crystallographic databases
Acta Cryst. Volume B58, Part 3 Number 1 (pp. 317-422, 1 June 2002)

Crystallographic databases
Acta Cryst. Volume D58, Part 6 Number 1 (pp. 879-920, 1 June 2002)

Fifth Harima International Forum on New Aspects of X-ray Imaging Technology with Synchrotron Radiation - Present Status and Future Possibilities, HIF2001, Harima Science Garden City, Japan, 12-14 July 2001
J. Synchrotron Rad. Volume 9, Part 3 (pp. 107-188, 1 May 2002)

CCP4 Study Weekend on Molecular Replacement and its Relatives, York, UK, January 2001
Acta Cryst. Volume D57, Part 10 (pp. 1355-1490, 1 October 2001)

Eleventh International Conference on X-ray Absorption Fine Structure, XAFS XI, Ako, Japan, 26-31 July 2000
J. Synchrotron Rad. Volume 8, Part 2 (pp. 47-1014, 1 March 2001)

CCP4 Study Weekend on Low-Resolution Phasing, York, UK, January 2000
Acta Cryst. Volume D56, Part 10 (pp. 1205-1357, 1 October 2000)

11th International Conference on Small-Angle Scattering, Brookhaven National Laboratory, USA, 17-20 May 1999
J. Appl. Cryst. Volume 33, Part 3 Number 1 (pp. 421-868, 1 June 2000)

Synchrotron Radiation Satellite Meeting of the XVIII IUCr Congress, Daresbury Laboratory, UK, 1-4 August 1999
J. Synchrotron Rad. Volume 7, Part 3 (pp. 115-202, 1 May 2000)

CCP4 Study Weekend on Data Collection and Processing, Sheffield, UK, January 1999
Acta Cryst. Volume D55, Part 10 (pp. 1631-1772, 1 October 1999)

CCP4 Study Weekend on Databases for Macromolecular Crystallographers, Reading, UK, January 1998
Acta Cryst. Volume D54, Part 6, Number 1 (pp. 1065-1206, 1 November 1998)



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