John Kendrick

University of Bradford, Chemistry, Emeritus

Followers

Following

Co-authors

Mentions

Public Views

Interests

Uploads

Papers by John Kendrick

$Research paper thumbnail of Understanding the Effect of Dispersion Corrections on the Calculated Spectra of $\alpha$-Lactose Monohydrate$

Understanding the Effect of Dispersion Corrections on the Calculated Spectra of $\alpha$-Lactose Monohydrate

2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

This is a repository copy of Understanding the Effect of Dispersion Corrections on the Calculated... more

Download

Coformer Replacement as an Indicator for Thermodynamic Instability of Cocrystals: Competitive Transformation of Caffeine:Dicarboxylic Acid

Crystal Growth & Design, 2016

The thermodynamic stability of caffeine (CA) cocrystals with dicarboxylic acids (DAs) as coformer... more The thermodynamic stability of caffeine (CA) cocrystals with dicarboxylic acids (DAs) as coformers was investigated in the presence of a range of structurally related dicarboxylic acids (SRDs). Two experimental conditions (slurry and dry-grinding) were studied for mixing the cocrystal and the SRD additive. The additives oxalic, malonic and glutaric acid led to the replacement of the acid coformer for certain cocrystals. Interestingly, a change in stoichiometry was observed for the CA:maleic acid system. A stability order among the energy level. Therefore, kinetic experiments, such as quantitative phase analysis, can be performed to obtain a deeper knowledge about the mechanism.

Download

LETTERS Cooperative mechanisms of fast-ion

conduction in gallium-based oxides with tetrahedral moieties

Download

Significant progress in predicting the crystal structures of small organic molecules – a report on the fourth blind test

Acta Crystallographica Section B Structural Science, 2009

We report on the organization and outcome of the fourth blind test of crystal structure predictio... more We report on the organization and outcome of the fourth blind test of crystal structure prediction, an international collaborative project organized to evaluate the present state in computational methods of predicting the crystal structures of small organic molecules. There were 14 research groups which took part, using a variety of methods to generate and rank the most likely crystal structures for four target systems: three single-component crystal structures and a 1:1 cocrystal. Participants were challenged to predict the crystal structures of the four systems, given only their molecular diagrams, while the recently determined but as-yet unpublished crystal structures were withheld by an independent referee. Three predictions were allowed for each system. The results demonstrate a dramatic improvement in rates of success over previous blind tests; in total, there were 13 successful predictions and, for each of the four targets, at least two groups correctly predicted the observed...

Download

Calculating the Complex Permittivity of Powdered Crystalline Materials

Solid-state density functional theory calculations including periodic boundary conditions have be... more Solid-state density functional theory calculations including periodic boundary conditions have become well established for calculating the THz spectra of crystalline materials. Here we compare a range of DFT programs and calculation parameters including a number of van der Waals’ dispersive corrections in combination with our post-processing tool, PDielec, to calculate the complex permittivity of a range of powdered crystalline materials.

Combining crystal structure prediction and structural comparison with experimental screening: a potential route to more polymorphs, including a 2-for-the-price-of-1 special

Acta Crystallographica Section A Foundations and Advances

Download

Experimental and theoretical investigations of the polymorphism of 5-chloroacetoxybenzoic acid (5-chloroaspirin)

CrystEngComm

From an initial crystallographic study of a large family of ring-substituted 2-acetoxybenzoic aci... more From an initial crystallographic study of a large family of ring-substituted 2-acetoxybenzoic acids, only one member - the 5-chloro derivative - showed polymorphism, with two forms (α and β) identified, the former having a marginally higher melting point. The two structures show a close 1-D similarity through a row of carboxylic dimers connected via ClO halogen bonds, which assemble to give an approximate 2-D similarity by the stacking of these rows in a second direction. However, the further packing arrangement of the resulting 2-D stacks is significantly different in the two forms, through different symmetry arrangements and subtle variations in C–HO weak hydrogen bonds. A parallel crystal structure prediction (CSP) calculation identified the two experimental polymorphs in the correct stability order with effective energy rankings of 2 and 3 (lattice energy difference of 0.2 kcal mol−1). The lowest energy crystal structure found during the CSP, as yet not found experimentally, is ...

Generalised Atomic and Molecular Electronic Structure System

Additional key references and background material on each of the modules are provided at appropri... more

Download

Towards crystal structure prediction of complex organic compounds – a report on the fifth blind test

Acta Crystallographica Section B Structural Science, 2011

Following on from the success of the previous crystal structure prediction blind tests (CSP1999, ... more Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories – a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their fi...

Download

Molecular Properties: Proceedings of the CCP-1 Study Weekend

Correction to: Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Journal of Infrared, Millimeter, and Terahertz Waves

Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Journal of Infrared, Millimeter, and Terahertz Waves

A number of DFT programs with various combinations of pseudo-potentials and van der Waals’ disper... more A number of DFT programs with various combinations of pseudo-potentials and van der Waals’ dispersive corrections have been used to optimize the structure of sodium peroxodisulfate, Na2(SO4)2, and to calculate the infrared, attenuated total reflectance and terahertz absorption spectra of the powdered crystal. Comparison of the results from the different methods highlights the problems of calculating the absorption spectrum reliably. In particular the low frequency phonon modes are especially sensitive to the choice of grids to represent the wavefunction or the charge distribution, k-point integration grid and the energy cutoff. A comparison is made between the Maxwell-Garnett (MG) and Bruggeman effective medium methods used to account for the effect of crystal shape on the predicted spectrum. Possible scattering of light by air inclusions in the sample and by larger particles of Na2(SO4)2 is also considered using the Mie method. The results of the calculations are compared with expe...

The Calculation of the Infrared and Terahertz Spectrum of Sodium Peroxodisulfate

A number of DFT programs with various combinations of pseudo-potentials and van der Waals’ disper... more A number of DFT programs with various combinations of pseudo-potentials and van der Waals’ dispersive corrections have been used to optimize the structure of sodium peroxodisulfate, Na2(SO4)2, and to calculate the infra-red and terahertz absorption spectrum of the powdered crystal. Comparison of the results from the different methods highlights the problems of calculating the absorption spectrum reliably. In particular the low frequency phonon modes are especially sensitive to the choice of grids to represent the wavefunction or the charge distribution, k-point integration grid and the energy cutoff. A comparison is made between the Maxwell-Garnett (MG) and Bruggeman effective medium methods used to account for the effect of crystal shape on the predicted spectrum. Possible scattering of light by air inclusions in the sample and by larger particles of Na2(SO4)2 is also considered using the Mie method. The results of the calculations are compared with experimental measurements of the...

Report on the sixth blind test of organic crystal structure prediction methods

Acta crystallographica Section B, Structural science, crystal engineering and materials, Aug 1, 2016

The sixth blind test of organic crystal structure prediction (CSP) methods has been held, with fi... more The sixth blind test of organic crystal structure prediction (CSP) methods has been held, with five target systems: a small nearly rigid molecule, a polymorphic former drug candidate, a chloride salt hydrate, a co-crystal and a bulky flexible molecule. This blind test has seen substantial growth in the number of participants, with the broad range of prediction methods giving a unique insight into the state of the art in the field. Significant progress has been seen in treating flexible molecules, usage of hierarchical approaches to ranking structures, the application of density-functional approximations, and the establishment of new workflows and `best practices' for performing CSP calculations. All of the targets, apart from a single potentially disordered Z' = 2 polymorph of the drug candidate, were predicted by at least one submission. Despite many remaining challenges, it is clear that CSP methods are becoming more applicable to a wider range of real systems, including s...

A configuration interaction calculation of the potential energy surface of Li3

Mol Phys, 1977

Theoretical interpretation of 1s hole satellite peaks of formaldehyde

J Electron Spectrosc Relat Ph, 1975

Configuration interaction calculations of the satellite peaks associated with CIS ionization of carbon monoxide

A theoretical study, including correlation, of the low-lying states of the ethynyl radical

Mol Phys, 1975

Experimental and theoretical investigations of the polymorphism of 5-chloroacetoxybenzoic acid (5-chloroaspirin)

Crystengcomm, Feb 6, 2012

Calculation and Measurement of Terahertz Active Normal Modes in Crystalline PETN

Chemphyschem, Feb 1, 2010

$Research paper thumbnail of Understanding the Effect of Dispersion Corrections on the Calculated Spectra of $\alpha$-Lactose Monohydrate$

Understanding the Effect of Dispersion Corrections on the Calculated Spectra of $\alpha$-Lactose Monohydrate

2020 45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)

This is a repository copy of Understanding the Effect of Dispersion Corrections on the Calculated... more

Download

Coformer Replacement as an Indicator for Thermodynamic Instability of Cocrystals: Competitive Transformation of Caffeine:Dicarboxylic Acid

Crystal Growth & Design, 2016

Download

LETTERS Cooperative mechanisms of fast-ion

conduction in gallium-based oxides with tetrahedral moieties

Download

Significant progress in predicting the crystal structures of small organic molecules – a report on the fourth blind test

Acta Crystallographica Section B Structural Science, 2009

Download

Calculating the Complex Permittivity of Powdered Crystalline Materials

Combining crystal structure prediction and structural comparison with experimental screening: a potential route to more polymorphs, including a 2-for-the-price-of-1 special

Acta Crystallographica Section A Foundations and Advances

Download

Experimental and theoretical investigations of the polymorphism of 5-chloroacetoxybenzoic acid (5-chloroaspirin)

CrystEngComm

Generalised Atomic and Molecular Electronic Structure System

Additional key references and background material on each of the modules are provided at appropri... more

Download

Towards crystal structure prediction of complex organic compounds – a report on the fifth blind test

Acta Crystallographica Section B Structural Science, 2011

Download

Molecular Properties: Proceedings of the CCP-1 Study Weekend

Correction to: Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Journal of Infrared, Millimeter, and Terahertz Waves

Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Journal of Infrared, Millimeter, and Terahertz Waves

The Calculation of the Infrared and Terahertz Spectrum of Sodium Peroxodisulfate

A number of DFT programs with various combinations of pseudo-potentials and van der Waals’ disper... more A number of DFT programs with various combinations of pseudo-potentials and van der Waals’ dispersive corrections have been used to optimize the structure of sodium peroxodisulfate, Na2(SO4)2, and to calculate the infra-red and terahertz absorption spectrum of the powdered crystal. Comparison of the results from the different methods highlights the problems of calculating the absorption spectrum reliably. In particular the low frequency phonon modes are especially sensitive to the choice of grids to represent the wavefunction or the charge distribution, k-point integration grid and the energy cutoff. A comparison is made between the Maxwell-Garnett (MG) and Bruggeman effective medium methods used to account for the effect of crystal shape on the predicted spectrum. Possible scattering of light by air inclusions in the sample and by larger particles of Na2(SO4)2 is also considered using the Mie method. The results of the calculations are compared with experimental measurements of the...

Report on the sixth blind test of organic crystal structure prediction methods

Acta crystallographica Section B, Structural science, crystal engineering and materials, Aug 1, 2016

A configuration interaction calculation of the potential energy surface of Li3

Mol Phys, 1977

Theoretical interpretation of 1s hole satellite peaks of formaldehyde

J Electron Spectrosc Relat Ph, 1975

Configuration interaction calculations of the satellite peaks associated with CIS ionization of carbon monoxide

A theoretical study, including correlation, of the low-lying states of the ethynyl radical

Mol Phys, 1975

Experimental and theoretical investigations of the polymorphism of 5-chloroacetoxybenzoic acid (5-chloroaspirin)

Crystengcomm, Feb 6, 2012

Calculation and Measurement of Terahertz Active Normal Modes in Crystalline PETN

Chemphyschem, Feb 1, 2010

John Kendrick

Uploads

Papers by John Kendrick

Log In