Keith Butler

Mr
Keith
Butler
Job Title
Office Phone Number
(01235) 446541
Yes
Email
keith.butler@stfc.ac.uk
No
Office Location
RAL R116,FirstFloor
Yes
Mobile Phone Number
No

​Contact

keith.butler@stfc.ac.uk

Biography

I am a senior data scientist in the SciML team, with a focus on machine learning for materials science projects. My background is in computational materials science, he has experience in a range of different topics inclduing modelling and design of energy materials, simulations to help understand scattering and spectroscopic experimental data and designing virtual high-throughput screening workflows combining machine learning and first-principles approaches. Iobtained a degree in Chemistry from Trinity College Dublin and a PhD in Computational Chemistry from UCL. I previously worked at ISIS, the University of Bath and the Univeristy of Sheffield.

Research interests

My research interestes centre on the application of machine learning to solve problems in materials science.

  • Surrogate models to speed up simulations and materials design
  • Explainable machine learning models to understand the resutls of data-driven models
  • Uncertainty quantification and active learning for materials science
  • Unsupervised learning and clustering to classify experimental and numerical data

Publications

[1] T. Hey, K. Butler, S. Jackson, and J. Thiyagalingam, Machine learning and big scienti c data, Philosophical Transactions of the Royal Society A 378, 20190054 (2020).
[2] J. Armstrong, A. J. O'Malley, M. R. Ryder, and K. T. Butler, Understanding dynamic properties of materials using neutron spectroscopy and atomistic simulation, Journal of Physics Communications (2020).

[3] K. Morita, D. W. Davies, K. T. Butler, and A. Walsh, Modelling the dielectric constants of  crystals using machine learning, arXiv preprint arXiv:2005.05831 (2020).
[4] D. Bodesheim, G. Kieslich, M. Johnson, and K. T. Butler, Understanding the balance of entropy and enthalpy in hydrogen{halide noncovalent bonding, The Journal of Physical Chemistry Letters 11, 3495 (2020).

[5] A. Nearchou, J. Armstrong, K. Butler, P. R. Raithby, and A. Sartbaeva, Di erentiating the role of organic additives to assemble open framework aluminosilicate zeolites using ins spectroscopy, Physical Chemistry Chemical Physics (2020).

6] H.Wang, J. Jia, L.Wang, K. Butler, R. Song, G. Casillas, L. He, N. P. Kherani, D. D. Perovic, L. Jing, et al., CO2 photoreduction: Heterostructure engineering of a reverse water gas shiftphotocatalyst, Advanced Science 6, 1970134 (2019).
 [7] K. T. Butler, G. S. Gautam, and P. Canepa, Designing interfaces in energy materials applicationswith first-principles calculations, npj Computational Materials 5, 1 (2019).
[8] R. Dorin, L. D. Filip, L. Pintilie, K. T. Butler, and N. Plugaru, Designing functional ferroelectric interfaces from rst-principles: dipoles and band bending at oxide heterojunctions, New Journal of Physics 21, 113005 (2019).
[9] K. T. Butler, P. Vervoorts, M. G. Ehrenreich, J. Armstrong, J. M. Skelton, and G. Kieslich, Experimental evidence for vibrational entropy as driving parameter of
flexibility in the metal organic framework zif-4 (zn), Chemistry of Materials 31, 8366 (2019).

[10] M. J. Wahila, Z. W. Lebens-Higgins, K. T. Butler, D. Fritsch, R. E. Treharne, R. G. Palgrave, J. C.Woicik, B. J. Morgan, A.Walsh, and L. F. Piper, Accelerated optimization of transparent,amorphous zinc-tin-oxide thin lms for optoelectronic applications, APL Materials 7, 022509 (2019).
[11] C. N. Singh, K. T. Butler, A. H. MacDonald, L. F. Piper, and W.-C. Lee, Dynamic disorder induced memristance in amorphous solids, arXiv preprint arXiv:1908.08070 (2019).
[12] R. Pandey, G. Vats, J. Yun, C. R. Bowen, A. W. Ho-Baillie, J. Seidel, K. T. Butler, and S. I. Seok, Mutual insight on ferroelectrics and hybrid halide perovskites: a platform for future multifunctional energy conversion, Advanced Materials 31, 1807376 (2019).
[13] S. K. Wallace, K. T. Butler, Y. Hinuma, and A. Walsh, Finding a junction partner for candidate solar cell absorbers enargite and bournonite from electronic band and lattice matching, Journal of Applied Physics 125, 055703 (2019).
[14] S. M. Collins, D. M. Kepaptsoglou, K. Butler, L. Longley, J. Hou, T. D. Bennett, Q. Ramasse,  and P. Midgley, Local coordination in metal-organic frameworks probed in the vibrational and optical regime by eels, Microscopy and Microanalysis 25, 606 (2019).
[15] T. W. Kasel, Z. Deng, A. M. Mroz, C. H. Hendon, K. T. Butler, and P. Canepa, Metal-free perovskites for non linear optical materials, Chemical Science 10, 8187 (2019).
 [16] D. W. Davies, K. T. Butler, A. J. Jackson, J. M. Skelton, K. Morita, and A. Walsh, Smact:Semiconducting materials by analogy and chemical theory, Journal of Open Source Software 4, 1361 (2019).

[17] C. Schneider, D. Bodesheim, M. G. Ehrenreich, V. Crocella, J. Mink, R. A. Fischer, K. T. Butler, and G. Kieslich, Tuning the negative thermal expansion behavior of the metal-organic framework Cu3btc2 by retrofi tting, Journal of the American Chemical Society 141, 10504 (2019).
[18] D. W. Davies, K. T. Butler, and A. Walsh, Data-driven discovery of photoactive quaternary oxides using first-principles machine learning, Chemistry of Materials 31, 7221 (2019).
[19] K. T. Butler, D. W. Davies, H. Cartwright, O. Isayev, and A. Walsh, Machine learning for molecular and materials science, Nature 559, 547 (2018).
[20] W. Wei, W. Li, K. T. Butler, G. Feng, C. J. Howard, M. A. Carpenter, P. Lu, A. Walsh, and A. K. Cheetham, An unusual phase transition driven by vibrational entropy changes in a hybrid organic-inorganic perovskite, Angewandte Chemie 130, 9070 (2018).
[21] M. Makaremi, S. Grixti, K. T. Butler, G. A. Ozin, and C. V. Singh, Band engineering of carbon nitride monolayers by n-type, p-type, and isoelectronic doping for photocatalytic applications, ACS applied materials & interfaces 10, 11143 (2018).
[22] D. W. Davies, K. T. Butler, O. Isayev, and A.Walsh, Materials discovery by chemical analogy: role of oxidation states in structure prediction, Faraday Discussions 211, 553 (2018).
[23] S. M. Collins, D. M. Kepaptsoglou, K. T. Butler, L. Longley, T. D. Bennett, Q. M. Ramasse, and P. A. Midgley, Subwavelength spatially resolved coordination chemistry of metal-organic framework glass blends, Journal of the American Chemical Society 140, 17862 (2018).
[24] K. T. Butler, D. W. Davies, and A. Walsh, Computational design of photovoltaic materials, in Computational Materials Discovery (2018) pp. 176-197.
[25] G. Kieslich, J. M. Skelton, J. Armstrong, Y. Wu, F. Wei, K. L. Svane, A. Walsh, and K. T. Butler, Hydrogen bonding versus entropy: revealing the underlying thermodynamics of the hybrid organic-inorganic perovskite [CH3NH3] PbBr3, Chemistry of Materials 30, 8782 (2018).
[26] K. T. Butler, The chemical forces underlying octahedral tilting in halide perovskites, Journal of Materials Chemistry C 6, 12045 (2018).
[27] J.-S. Park, Y.-K. Jung, K. T. Butler, and A. Walsh, Quick-start guide for fi rst-principles modelling of semiconductor interfaces, Journal of Physics: Energy 1, 016001 (2018).
[28] D. W. Davies, K. T. Butler, J. M. Skelton, C. Xie, A. R. Oganov, and A. Walsh, Computer aided design of metal chalcohalide semiconductors: from chemical composition to crystal structure, Chemical science 9, 1022 (2018).

[29] K. L. Svane, A. C. Forse, C. P. Grey, G. Kieslich, A. K. Cheetham, A.Walsh, and K. T. Butler, How strong is the hydrogen bond in hybrid perovskites?, The journal of physical chemistry letters 8, 6154 (2017).
[30] T. Banerjee, T. Bennett, K. Butler, T. L. Easun, M. Eddaoudi, R. Forgan, L. Gagliardi, C. Hendon, M. Jorge, C. Lamberti, et al., Electronic, magnetic and photophysical properties of mofs and cofs: general discussion, Faraday Discussions 201, 87 (2017).
[31] M. Addicoat, K. Butler, O. Farha, L. Gagliardi, A. H. Farmahini, C. Hendon, M. Jorge, S. Kitagawa, C. Lamberti, J.-S. M. Lee, et al., Mofs modeling and theory: general discussion, Faraday Discussions 201, 233 (2017).
[32] K. T. Butler, S. D. Worrall, C. D. Molloy, C. H. Hendon, M. P. Att eld, R. A. Dryfe, and A. Walsh, Electronic structure design for nanoporous, electrically conductive zeolitic imidazolate frameworks, Journal of Materials Chemistry C 5, 7726 (2017).
[33] J. Jia, C. Qian, Y. Dong, Y. F. Li, H. Wang, M. Ghoussoub, K. T. Butler, A. Walsh, and G. A. Ozin, Heterogeneous catalytic hydrogenation of co 2 by metal oxides: defect engineering: perfecting imperfection, Chemical Society Reviews 46, 4631 (2017).
[34] H. Sepehri-Amin, H. Iwama, G. Hrkac, K. Butler, T. Shima, and K. Hono, Pt surface segregation in l10-fept nano-grains, Scripta Materialia 135, 88 (2017).
[35] N. Plugaru, G. A. Nemnes, L. Filip, I. Pintilie, L. Pintilie, K. T. Butler, and A. Manolescu, Atomistic simulations of methylammonium lead halide layers on PbTiO3 (001) surfaces, The Journal of Physical Chemistry C 121, 9096 (2017).
[36] C. H. Hendon, K. T. Butler, A. M. Ganose, Y. Roman-Leshkov, D. O. Scanlon, G. A. Ozin, and A. Walsh, Electroactive nanoporous metal oxides and chalcogenides by chemical design, Chemistry of Materials 29, 3663 (2017).
[37] J. K. Bristow, K. T. Butler, K. L. Svane, J. D. Gale, and A. Walsh, Chemical bonding at the metal-organic framework/metal oxide interface: simulated epitaxial growth of MOF-5 on rutile TiO2, Journal of Materials Chemistry A 5, 6226 (2017).
[38] Y. Kumagai, K. T. Butler, A. Walsh, and F. Oba, Theory of ionization potentials of nonmetallic solids, Physical Review B 95, 125309 (2017).
[39] K. T. Butler, C. H. Hendon, and A. Walsh, Designing porous electronic thin- lm devices: band o sets and heteroepitaxy, Faraday Discussions 201, 207 (2017).
[40] Y.-K. Jung, K. T. Butler, and A. Walsh, Halide perovskite heteroepitaxy: bond formation and carrier con nement at the PbS:CsPbBr3 interface, The Journal of Physical Chemistry C 121, 27351 (2017).
[41] C. H. Hendon, F. Pradaux-Caggiano, L. E. Hatcher, W. J. Gee, C. C. Wilson, K. T. Butler, D. R. Carbery, A. Walsh, and B. C. Melot, Magnetic coupling in a hybrid mn (ii) acetylene dicarboxylate, Physical Chemistry Chemical Physics 18, 33329 (2016).
[42] K. Butler, B. Dringoli, L. Zhou, P. Rao, A. Walsh, and L. Titova, Ultrafast carrier dynamicsin BiVO4 thin film photoanode material: interplay between free carriers, trapped carriers andlow-frequency lattice vibrations, Journal of Materials Chemistry A 4, 18516 (2016).
[43] C. H. Hendon, S. T. Hunt, M. Milina, K. T. Butler, A. Walsh, and Y. Roman-Leshkov, Realistic surface descriptions of heterometallic interfaces: the case of TiWC coated in noble metals, The Journal of Physical Chemistry Letters 7, 4475 (2016).
[44] D. W. Davies, K. T. Butler, A. J. Jackson, A. Morris, J. M. Frost, J. M. Skelton, and A.Walsh, Computational screening of all stoichiometric inorganic materials, Chem 1, 617 (2016).
[45] K. T. Butler, K. Svane, G. Kieslich, A. K. Cheetham, and A. Walsh, Microscopic origin of entropy-driven polymorphism in hybrid organic-inorganic perovskite materials, Physical Review B 94, 180103 (2016).
[46] K. T. Butler, J. M. Frost, J. M. Skelton, K. L. Svane, and A. Walsh, Computational materials design of crystalline solids, Chemical Society Reviews 45, 6138 (2016).
[47] K. T. Butler, S. McKechnie, P. Azarhoosh, M. Van Schilfgaarde, D. O. Scanlon, and A. Walsh, Quasi-particle electronic band structure and alignment of the v-vi-vii semiconductors SbSI, SbSBr, and SbSeI for solar cells, Applied Physics Letters 108, 112103 (2016).
[48] A. M. Ganose, M. Cu , K. T. Butler, A. Walsh, and D. O. Scanlon, Interplay of orbital and relativistic effects in bismuth oxyhalides: BioF, BiOCl, BiOBr, and BiOI, Chemistry of Materials 28, 1980 (2016).
[49] M. Wahila, Z. Lebens-Higgins, N. Quackenbush, L. Piper, K. Butler, C. Hendon, A. Walsh, and G. Watson, Hole conduction pathways in transparent amorphous tin oxides, APS 2016,L26 (2016).
[50] A. M. Ganose, K. T. Butler, A. Walsh, and D. O. Scanlon, Relativistic electronic structure and band alignment of BiSI and BiSeI: candidate photovoltaic materials, Journal of Materials Chemistry A 4, 2060 (2016).
[51] K. T. Butler, Y. Kumagai, F. Oba, and A. Walsh, Screening procedure for structurally and electronically matched contact layers for high-performance solar cells: hybrid perovskites, Journal of Materials Chemistry C 4, 1149 (2016).
[52] K. T. Butler, A. Walsh, A. K. Cheetham, and G. Kieslich, Organised chaos: entropy in hybrid inorganic-organic systems and other materials, Chemical science 7, 6316 (2016).
[53] M. J. Wahila, K. T. Butler, Z. W. Lebens-Higgins, C. H. Hendon, A. S. Nandur, R. E. Treharne, N. F. Quackenbush, S. Sallis, K. Mason, H. Paik, et al., Lone-pair stabilization in transparent amorphous tin oxides: a potential route to p-type conduction pathways, Chemistry of Materials 28, 4706 (2016).
[54] G. Kieslich, A. C. Forse, S. Sun, K. T. Butler, S. Kumagai, Y. Wu, M. R. Warren, A. Walsh, C. P. Grey, and A. K. Cheetham, Role of amine-cavity interactions in determining the structureand mechanical properties of the ferroelectric hybrid perovskite [NH3NH2] Zn(HCOO) 3,Chemistry of Materials 28, 312 (2016).
[55] E. Uman, M. Colonna-Dashwood, L. Colonna-Dashwood, M. Perger, C. Klatt, S. Leighton, B. Miller, K. T. Butler, B. C. Melot, R. W. Speirs, et al., The e ect of bean origin and temperature on grinding roasted co ee, Scienti c reports 6, 24483 (2016).
[56] B. J. Dringoli, K. T. Butler, L. Zhou, B. Giri, P. M. Rao, A. Walsh, and L. V. Titova, Ultrafast carrier dynamics in BiVO4: Interplay between free carriers, trapped carriers and low frequency lattice vibrations, in 2016 41st International Conference on Infrared, Millimeter,
and Terahertz waves (IRMMW-THz) (IEEE, 2016) pp. 1-2.
[57] A.Walsh, K. T. Butler, and C. H. Hendon, Chemical principles for electroactive metal-organic frameworks, MRS Bulletin 41, 870 (2016).
[58] K. T. Butler, J. M. Frost, and A. Walsh, Band alignment of the hybrid halide perovskites CH3NH3PbCl3, CH3NH3PbBr3 and CH3NH3PbI3, Materials Horizons 2, 228 (2015).
[59] G. Hrkac, P. S. Keatley, M. T. Bryan, and K. Butler, Magnetic vortex oscillators, Journal of Physics D: Applied Physics 48, 453001 (2015).
[60] P. J. Isherwood, K. T. Butler, A.Walsh, and J. M.Walls, A tunable amorphous p-type ternary oxide system: The highly mismatched alloy of copper tin oxide, Journal of Applied Physics 118, 105702 (2015).
[61] G. Kieslich, S. Kumagai, K. T. Butler, T. Okamura, C. H. Hendon, S. Sun, M. Yamashita, A. Walsh, and A. K. Cheetham, Role of entropic effects in controlling the polymorphism informate ABX3 metal-organic frameworks, Chemical communications 51, 15538 (2015).

[62] A. J. Jackson, J. M. Skelton, C. H. Hendon, K. T. Butler, and A. Walsh, Crystal structure optimisation using an auxiliary equation of state, The Journal of chemical physics 143, 184101 (2015).
[63] J. Buckeridge, K. T. Butler, C. R. A. Catlow, A. J. Logsdail, D. O. Scanlon, S. A. Shevlin, S. M. Woodley, A. A. Sokol, and A. Walsh, Polymorph engineering of tio2: demonstrating how absolute reference potentials are determined by local coordination, Chemistry of Materials 27,3844 (2015).
[64] K. T. Butler, Morphological control of band o sets for transparent bipolar heterojunctions: The badeker diode, physica status solidi (a) 212, 1461 (2015).
[65] C. H. Hendon, K. E. Wittering, T.-H. Chen, W. Kaveevivitchai, I. Popov, K. T. Butler, C. C. Wilson, D. L. Cruickshank, O. S. Miljanic, and A. Walsh, Absorbate-induced piezochromism in a porous molecular crystal, Nano letters 15, 2149 (2015).
[66] C.-E. Kim, Y.-J. Tak, K. T. Butler, A.Walsh, and A. Soon, Lattice-mismatched heteroepitaxy of IV-VI thin lms on pbte (001): An ab initio study, Physical Review B 91, 085307 (2015).
[67] K. T. Butler, J. M. Frost, and A. Walsh, Ferroelectric materials for solar energy conversion: photoferroics revisited, Energy & Environmental Science 8, 838 (2015).
[68] R. X. Yang, K. T. Butler, and A. Walsh, Assessment of hybrid organic-inorganic antimony sul des for earth-abundant photovoltaic applications, The journal of physical chemistry letters 6, 5009 (2015).
[69] S. Sallis, K. Butler, N. Quackenbush, D. Williams, M. Junda, D. Fischer, J. Woicik, N. Podraza, B. White Jr, A. Walsh, et al., Origin of deep subgap states in amorphous indium gallium zinc oxide: Chemically disordered coordination of oxygen, Applied Physics Letters 104, 232108 (2014).
[70] G. Hrkac, K. Butler, T. Woodcock, L. Saharan, T. Schreffel, and O. Guteflisch, Modeling of Nd-oxide grain boundary phases in Nd-Fe-B sintered magnets, JOM 66, 1138 (2014).
[71] S.-H. Yoo, K. T. Butler, A. Soon, A. Abbas, J. M.Walls, and A.Walsh, Identi cation of critical stacking faults in thin- lm CdTesolar cells, Applied Physics Letters 105, 062104 (2014).
[72] K. T. Butler, C. H. Hendon, and A. Walsh, Electronic chemical potentials of porous metal-organic frameworks, Journal of the American Chemical Society 136, 2703 (2014).
[73] J. M. Frost, K. T. Butler, and A. Walsh, Molecular ferroelectric contributions to anomalous hysteresis in hybrid perovskite solar cells, Apl Materials 2, 081506 (2014).

​​[74] A. M. Svensson, S. Olibet, D. Rudolph, E. Cabrera, J. Friis, K. Butler, and J. Harding, Contact resistance of screen printed ag-contacts to si emitters: Mathematical modeling andmicrostructural characterization, Journal of The Electrochemical Society 161, E3180 (2014).
[75] K. T. Butler, J. Buckeridge, C. R. A. Catlow, and A. Walsh, Crystal electron binding energy and surface work function control of tin dioxide, Physical Review B 89, 115320 (2014).
[76] J. M. Frost, K. T. Butler, F. Brivio, C. H. Hendon, M. Van Schilfgaarde, and A. Walsh, Atomistic origins of high-performance in hybrid halide perovskite solar cells, Nano letters 14, 2584 (2014).
[77] F. Brivio, K. T. Butler, A. Walsh, and M. Van Schilfgaarde, Relativistic quasiparticle self consistent electronic structure of hybrid halide perovskite photovoltaic absorbers, Physical Review B 89, 155204 (2014).
[78] M. Lamers, L. E. Hintzsche, K. T. Butler, P. E. Vullum, C.-M. Fang, M. Marsman, G. Jordan, J. H. Harding, G. Kresse, and A. Weeber, The interface of a-sinx: H and Si: Linking the nano scale structure to passivation quality, Solar energy materials and solar cells 120, 311 (2014).
[79] K. T. Butler and A. Walsh, Ultra-thin oxide fi lms for band engineering: design principles and numerical experiments, Thin Solid Films 559, 64 (2014).
[80] A. Walsh and K. T. Butler, Prediction of electron energies in metal oxides, Accounts of chemical research 47, 364 (2014).
[81] G. Hrkac, T. Woodcock, K. Butler, L. Saharan, M. Bryan, T. Schreffel, and O. Gutfleisch,
Impact of different Nd-rich crystal-phases on the coercivity of Nd-Fe-B grain ensembles, Scripta Materialia 70, 35 (2014).
[82] A. Weeber, M. Lamers, K. Butler, J. Harding, and P. Vullum, Characterization of a-SiNx: H layer: bulk properties, interface with Si and solar cell efficiency, (2013).
[83] A. P. Green, K. T. Butler, and A. R. Buckley, Tuning of the emission energy of fluorophores using solid state solvation for ecient luminescent solar concentrators, Applied Physics Letters 102, 133501 (2013).
[84] A. Weeber, M. Lamers, K. Butler, J. Harding, L. Hintzsche, C. Fang, M. Marsman, G. Jordan, G. Kresse, and P. Vullum, The interface of a-sinx: H and si: Linking the nano-scale structure to passivation quality, (2013).
[85] K. T. Butler and J. Harding, A computational investigation of nickel (silicides) as potential contact layers for silicon photovoltaic cells, Journal of Physics: Condensed Matter 25, 395003 (2013).
[86] M. Lamers, K. Butler, P. E. Vullum, J. Harding, and A. Weeber, Characterization of a-SiNx: H layer: Bulk properties, interface with si and solar cell eciency, physica status solidi (a) 210, 658 (2013).
[87] K. T. Butler and J. H. Harding, Atomistic simulation of doping effects on growth and charge transport in Si/Ag interfaces in high-performance solar cells, Physical Review B 86, 245319(2012).
[88] K. T. Butler, J. H. Harding, M. P. Lamers, and A. W. Weeber, Stoichiometrically graded SiNx for improved surface passivation in high performance solar cells, Journal of Applied Physics 112, 094303 (2012).
[89] M. W. Lamers, K. T. Butler, J. H. Harding, and A. Weeber, Interface properties of a-SiNx:H/Si to improve surface passivation, Solar energy materials and solar cells 106, 17 (2012).
[90] K. T. Butler and D. W. Lewis, Calculation of the 29Si NMR chemical shifts of aqueous silicate species, The Journal of Physical Chemistry A 116, 8786 (2012).
[91] A. Weeber, M. Lamers, K. Butler, and J. Harding, Interface properties of a-SiNx: H/Si to improve surface passivation, (2012).
[92] M. Lamers, K. Butler, I. G. Romijn, J. Harding, and A. W. Weeber, Examination of the properties of the interface of a-SiNx: H/Si in crystalline silicon solar cells and its effect on cell efficiency, in MRS Proceedings, Vol. 1423 (Cambridge University Press, 2012).
[93] K. T. Butler, P. E. Vullum, A. M. Muggerud, E. Cabrera, and J. H. Harding, Structural and electronic properties of silver/silicon interfaces and implications for solar cell performance, Physical Review B 83, 235307 (2011).
[94] K. T. Butler, M. P. Lamers, A. W. Weeber, and J. H. Harding, Molecular dynamics studies of the bonding properties of amorphous silicon nitride coatings on crystalline silicon, Journal of Applied Physics 110, 124905 (2011).
[95] A. Weeber, M. Lamers, K. Butler, and J. Harding, Molecular dynamics studies of the bonding properties of amorphous silicon nitride coatings on crystalline silicon, (2011).
[96] K. T. Butler, F. J. Luque, and X. Barril, Toward accurate relative energy predictions of the bioactive conformation of drugs, Journal of computational chemistry 30, 601 (2009).