Computational chemistry 6019 225829132 2008-07-15T16:19:29Z Epbr123 1395162 Reverted edits by [[Special:Contributions/OrgasGirl|OrgasGirl]] to last version by Bduke (using [[WP:HG|Huggle]]) '''Computational chemistry''' is a branch of [[chemistry]] that uses computers to assist in solving chemical problems. It uses the results of [[theoretical chemistry]], incorporated into efficient [[computer program]]s, to calculate the structures and properties of [[molecule]]s and solids. While its results normally complement the information obtained by chemical [[experiment]]s, it can in some cases predict hitherto unobserved chemical [[phenomena]]. It is widely used in the design of new drugs and materials. Examples of such properties are structure (i.e. the expected positions of the constituent atoms), absolute and [[interaction energy|relative]] (interaction) [[energy|energies]], [[electron]]ic [[charge density|charge distribution]]s, [[dipole]]s and higher [[multipole moment]]s, [[vibrational spectroscopy|vibrational frequencies]], [[reactivity]] or other [[spectroscopy|spectroscopic]] quantities, and [[cross section (physics)|cross sections]] for [[scattering theory|collision]] with other particles. The methods employed cover both static and dynamic situations. In all cases the computer time and other resources (such as memory and disk space) increase rapidly with the size of the system being studied. That system can be a single molecule, a group of molecules, or a solid. Computational chemistry methods range from highly accurate to very approximate; highly accurate methods are typically feasible only for small systems. [[Ab initio quantum chemistry methods|Ab initio]] methods are based entirely on theory from first principles. Other (typically less accurate) methods are called empirical or semi-empirical because they employ experimental results, often from acceptable models of atoms or related molecules, to approximate some elements of the underlying theory. Both ab initio and semi-empirical approaches involve approximations. These range from simplified forms of the first-principles equations that are easier or faster to solve, to approximations limiting the size of the system (for example, [[Periodic boundary conditions]]), to fundamental approximations to the underlying equations that are required to achieve any solution to them at all. For example, most ab initio calculations make the [[Born-Oppenheimer approximation]], which greatly simplifies the underlying [[Schroedinger Equation]] by freezing the nuclei in place during the calculation. In principle, [[Ab initio quantum chemistry methods|ab initio]] methods eventually converge to the exact solution of the underlying equations as the number of approximations is reduced. In practice, however, it is impossible to eliminate all approximations, and residual error inevitably remains. The goal of computational chemistry is to minimize this residual error while keeping the calculations tractable. ==History== Building on the founding discoveries and theories in the [[history of quantum mechanics]], the first theoretical calculations in chemistry were those of [[Walter Heitler]] and [[Fritz London]] in 1927. The books that were influential in the early development of computational quantum chemistry include: [[Linus Pauling]] and [[Edgar Bright Wilson|E. Bright Wilson]]’s 1935 ''Introduction to Quantum Mechanics – with Applications to Chemistry'', [[Henry Eyring|Eyring]], Walter and Kimball's 1944 ''Quantum Chemistry'', Heitler’s 1945 ''Elementary Wave Mechanics – with Applications to Quantum Chemistry'', and later [[Charles Coulson|Coulson]]'s 1952 textbook ''Valence'', each of which served as primary references for chemists in the decades to follow. With the development of efficient [[computer]] technology in the 1940s, the solutions of elaborate [[wave equation]]s for complex [[atom]]ic systems began to be a realizable objective. In the early 1950s, the first semi-empirical atomic orbital calculations were carried out. Theoretical chemists became extensive users of the early digital computers. A very detailed account of such use in the United Kingdom is given by Smith and Sutcliffe.<ref> {{cite journal | last = Smith | first = S. J. | coauthors = Sutcliffe B. T., | title = The development of Computational Chemistry in the United Kingdom | journal = Reviews in Computational Chemistry | volume = 70 | pages = 271–316 | date = 1997 }} </ref> The first ab initio [[Hartree-Fock]] calculations on diatomic molecules were carried out in 1956 at MIT, using a [[Basis set (chemistry)|basis set]] of [[Slater orbital]]s. For diatomic molecules, a systematic study using a minimum basis set and the first calculation with a larger basis set were published by Ransil and Nesbet respectively in 1960.<ref> {{cite book | last = Schaefer | first =Henry F. III | title = The electronic structure of atoms and molecules | publisher = Addison-Wesley Publishing Co. | date = 1972 | pages = 146 | location = Reading, Massachusetss }} </ref> The first polyatomic calculations using Gaussian orbitals were carried out in the late 1950s. The first [[configuration interaction]] calculations were carried out in Cambridge on the [[EDSAC]] computer in the 1950s using [[Gaussian orbital]]s by [[Francis Boys|Boys]] and coworkers.<ref>{{cite journal | last = Boys | first = S. F. | coauthors = Cook G. B., Reeves C. M., Shavitt, I. | title = Automatic fundamental calculations of molecular structure | journal = Nature | volume = 178 | issue = 2 | pages = 1207 | date = 1956 | doi = 10.1038/1781207a0 }} </ref> By 1971, when a bibliography of ab initio calculations was published,<ref> {{cite book | last = Richards | first =W. G. | coauthors = Walker T. E. H and Hinkley R. K. | title = A bibliography of ab initio molecular wave functions | publisher = Clarendon Press | date = 1971 | location = Oxford }} </ref> the largest molecules included were [[naphthalene]] and [[azulene]].<ref> Preuss, H. (1968). [[International Journal of Quantum Chemistry]] 2: 651. </ref> <ref> Buenker, R. J.; Peyerimhoff S. D. (1969). [[Chemical Physics Letters]] 3: 37. </ref> Abstracts of many earlier developments in ab initio theory have been published by Schaefer.<ref> {{cite book | last = Schaefer | first =Henry F. III | title = Quantum Chemistry | publisher = Clarendon Press | date = 1984 | location = Oxford }} </ref> In 1964, [[Hückel method]] calculations (using a simple [[linear combination of atomic orbitals]] (LCAO) method for the determination of electron energies of molecular orbitals of π electrons in conjugated hydrocarbon systems) of molecules ranging in complexity from [[butadiene]] and [[benzene]] to [[ovalene]], were generated on computers at Berkeley and Oxford.<ref> {{cite book | last = Streitwieser | first =A. | coauthors = Brauman J. I. and [[Charles Coulson|Coulson]] C. A. | title = Supplementary Tables of Molecular Orbital Calculations | publisher =Pergamon Press | date = 1965 | location = Oxford }} </ref> These empirical methods were replaced in the 1960s by [[Semi-empirical quantum chemistry method|semi-empirical methods]] such as [[CNDO/2|CNDO]].<ref> {{cite book | last = Pople | first = John A. | authorlink = John Pople | coauthors = David L. Beveridge | title = Approximate Molecular Orbital Theory | publisher = McGraw Hill | date = 1970 | location = New York }} </ref> In the early 1970s, efficient ab initio computer programs such as ATMOL, [[GAUSSIAN]], IBMOL, and POLYAYTOM, began to be used to speed up ab initio calculations of molecular orbitals. Of these four programs, only GAUSSIAN, now massively expanded, is still in use, but many other programs are now in use. At the same time, the methods of [[molecular mechanics]], such as [[MM2]], were developed, primarily by [[Norman Allinger]].<ref> {{cite journal | last = Allinger | first = Norman | authorlink = Norman Allinger | title = Conformational analysis. 130. MM2. A hydrocarbon force field utilizing V1 and V2 torsional terms | journal = Journal of the American Chemical Society | volume = 99 | pages = 8127–8134 | date = 1977 | doi = 10.1021/ja00467a001 }} </ref> One of the first mentions of the term “computational chemistry” can be found in the 1970 book ''Computers and Their Role in the Physical Sciences'' by Sidney Fernbach and Abraham Haskell Taub, where they state “It seems, therefore, that 'computational chemistry' can finally be more and more of a reality.”<ref>{{cite book | last = Fernbach | first = Sidney | coauthors = Taub, Abraham Haskell | title = Computers and Their Role in the Physical Sciences | publisher = Routledge | year = 1970 | id = ISBN 0677140304}}</ref> During the 1970s, widely different methods began to be seen as part of a new emerging discipline of ''computational chemistry''.<ref>[http://www3.interscience.wiley.com/cgi-bin/bookhome/114034476 Reviews in Computational Chemistry vol 1, preface]</ref> The ''[[Journal of Computational Chemistry]]'' was first published in 1980. == Concepts == The term ''theoretical chemistry'' may be defined as a mathematical description of chemistry, whereas ''computational chemistry'' is usually used when a mathematical method is sufficiently well developed that it can be automated for implementation on a computer. Note that the words ''exact'' and ''perfect'' do not appear here, as very few aspects of chemistry can be computed exactly. However, almost every aspect of chemistry can be described in a qualitative or approximate quantitative computational scheme. Molecules consist of nuclei and electrons, so the methods of [[quantum mechanics]] apply. Computational chemists often attempt to solve the non-relativistic [[Schrödinger equation]], with relativistic corrections added, although some progress has been made in solving the fully relativistic [[Dirac equation]]. In principle, it is possible to solve the Schrödinger equation in either its time-dependent or time-independent form, as appropriate for the problem in hand; in practice, this is not possible except for very small systems. Therefore, a great number of approximate methods strive to achieve the best trade-off between accuracy and computational cost. Accuracy can always be improved with greater computational cost. Significant errors can present themselves in ''ab initio'' models comprising of many electrons, due to the computational expense of full relativistic-inclusive methods. This complicates the study of molecules interacting with high atomic mass unit atoms, such as transitional metals and their catalytic properties. Present algorithms in computational chemistry can routinely calculate the properties of molecules that contain up to about 40 electrons with sufficient accuracy. Errors for energies can be less than a few kJ/mol. For geometries, bond lengths can be predicted within a few picometres and bond angles within 0.5 degrees. The treatment of larger molecules that contain a few dozen electrons is computationally tractable by approximate methods such as [[density functional theory]] (DFT). There is some dispute within the field whether or not the latter methods are sufficient to describe complex chemical reactions, such as those in biochemistry. Large molecules can be studied by semi-empirical approximate methods. Even larger molecules are treated by [[classical mechanics]] methods that employ what are called [[molecular mechanics]]. In QM/MM methods, small portions of large complexes are treated quantum mechanically (QM), and the remainder is treated approximately (MM). In theoretical chemistry, chemists, physicists and mathematicians develop [[algorithm]]s and computer programs to predict atomic and molecular properties and reaction paths for [[chemical reaction]]s. Computational chemists, in contrast, may simply apply existing computer programs and methodologies to specific chemical questions. There are two different aspects to computational chemistry: * Computational studies can be carried out in order to find a starting point for a laboratory synthesis, or to assist in understanding experimental data, such as the position and source of spectroscopic peaks. * Computational studies can be used to predict the possibility of so far entirely unknown molecules or to explore reaction mechanisms that are not readily studied by experimental means. Thus, computational chemistry can assist the experimental chemist or it can challenge the experimental chemist to find entirely new chemical objects. Several major areas may be distinguished within computational chemistry: * The prediction of the molecular structure of molecules by the use of the simulation of forces, or more accurate quantum chemical methods, to find stationary points on the energy surface as the position of the nuclei is varied. * Storing and searching for data on chemical entities (see [[chemical database]]s). * Identifying [[correlation]]s between [[chemical structure]]s and properties (see [[QSPR]] and [[QSAR]]). * Computational approaches to help in the efficient synthesis of compounds. * Computational approaches to design molecules that interact in specific ways with other molecules (e.g. [[drug design]] and [[catalysis]]). == Methods == A single molecular formula can represent a number of molecular isomers. Each isomer is a local minimum on the energy surface (called the [[potential energy surface]]) created from the total energy (i.e., the electronic energy, plus the repulsion energy between the nuclei) as a function of the coordinates of all the nuclei. A stationary point is a geometry such that the derivative of the energy with respect to all displacements of the nuclei is zero. A local (energy) minimum is a stationary point where all such displacements lead to an increase in energy. The local minimum that is lowest is called the global minimum and corresponds to the most stable isomer. If there is one particular coordinate change that leads to a decrease in the total energy in both directions, the stationary point is a [[Transition state|transition structure]] and the coordinate is the [[reaction coordinate]]. This process of determining stationary points is called geometry optimization. The determination of molecular structure by geometry optimization became routine only after efficient methods for calculating the first derivatives of the energy with respect to all atomic coordinates became available. Evaluation of the related second derivatives allows the prediction of vibrational frequencies if harmonic motion is estimated. More importantly, it allows for the characterization of stationary points. The frequencies are related to the eigenvalues of the Hessian matrix, which contains second derivatives. If the eigenvalues are all positive, then the frequencies are all real and the stationary point is a local minimum. If one eigenvalue is negative (i.e., an imaginary frequency), then the stationary point is a transition structure. If more than one eigenvalue is negative, then the stationary point is a more complex one, and is usually of little interest. When one of these is found, it is necessary to move the search away from it if the experimenter is looking solely for local minima and transition structures. The total energy is determined by approximate solutions of the time-dependent Schrödinger equation, usually with no relativistic terms included, and by making use of the [[Born-Oppenheimer approximation]], which allows for the separation of electronic and nuclear motions, thereby simplifying the Schrödinger equation. This leads to the evaluation of the total energy as a sum of the electronic energy at fixed nuclei positions and the repulsion energy of the nuclei. A notable exception are certain approaches called [[direct quantum chemistry]], which treat electrons and nuclei on a common footing. Density functional methods and semi-empirical methods are variants on the major theme. For very large systems, the relative total energies can be compared using molecular mechanics. The ways of determining the total energy to predict molecular structures are: === ''Ab initio'' methods === {{main|Ab initio quantum chemistry methods}} The programs used in computational chemistry are based on many different [[quantum chemistry|quantum-chemical]] methods that solve the molecular [[Schrödinger equation]] associated with the [[molecular Hamiltonian]]. Methods that do not include any empirical or semi-empirical parameters in their equations - being derived directly from theoretical principles, with no inclusion of experimental data - are called ''[[ab initio]]'' methods. This does not imply that the solution is an exact one; they are all approximate quantum mechanical calculations. It means that a particular approximation is rigorously defined on first principles (quantum theory) and then solved within an error margin that is qualitatively known beforehand. If numerical iterative methods have to be employed, the aim is to iterate until full machine accuracy is obtained (the best that is possible with a finite word length on the computer, and within the mathematical and/or physical approximations made). [[Image:Electron correlation.png|thumb|right|300px|Diagram illustrating various ''ab initio'' electronic structure methods in terms of energy. Spacings are not to scale.]] The simplest type of ''ab initio'' electronic structure calculation is the [[Hartree-Fock]] (HF) scheme, an extension of [[molecular orbital theory]], in which the correlated electron-electron repulsion is not specifically taken into account; only its average effect is included in the calculation. As the basis set size is increased, the energy and wave function tend towards a limit called the Hartree-Fock limit. Many types of calculations (known as [[post-Hartree-Fock]] methods) begin with a Hartree-Fock calculation and subsequently correct for electron-electron repulsion, referred to also as [[electronic correlation]]. As these methods are pushed to the limit, they approach the exact solution of the non-relativistic Schrödinger equation. In order to obtain exact agreement with experiment, it is necessary to include relativistic and [[Angular momentum coupling#Spin-orbit coupling|spin orbit]] terms, both of which are only really important for heavy atoms. In all of these approaches, in addition to the choice of method, it is necessary to choose a [[basis set (chemistry)|basis set]]. This is a set of functions, usually centered on the different atoms in the molecule, which are used to expand the molecular orbitals with the [[linear combination of atomic orbitals molecular orbital method|LCAO]] [[ansatz]]. Ab initio methods need to define a level of theory (the method) and a basis set. The Hartree-Fock wave function is a single configuration or determinant. In some cases, particularly for bond breaking processes, this is quite inadequate, and several [[Multi-configurational self-consistent field|configurations]] need to be used. Here, the coefficients of the configurations and the coefficients of the basis functions are optimized together. The total molecular energy can be evaluated as a function of the [[molecular geometry]]; in other words, the [[potential energy surface]]. Such a surface can be used for reaction dynamics. The stationary points of the surface lead to predictions of different [[isomer]]s and the [[Transition state theory|transition structure]]s for conversion between isomers, but these can be determined without a full knowledge of the complete surface. A particularly important objective, called computational [[thermochemistry]], is to calculate thermochemical quantities such as the [[Standard enthalpy change of formation|enthalpy of formation]] to chemical accuracy. Chemical accuracy is the accuracy required to make realistic chemical predictions and is generally considered to be 1 kcal/mol or 4 kJ/mol. To reach that accuracy in an economic way it is necessary to use a series of post-Hartree-Fock methods and combine the results. These methods are called [[quantum chemistry composite methods]]. === Density Functional methods === {{main|Density functional theory}} Density functional theory (DFT) methods are often considered to be ''[[ab initio]]'' methods for determining the molecular electronic structure, even though many of the most common [[Functional (mathematics)|functional]]s use parameters derived from empirical data, or from more complex calculations. This means that they could also be called semi-empirical methods. It is best to treat them as a class on their own. In DFT, the total energy is expressed in terms of the total one-[[electronic density|electron density]] rather than the wave function. In this type of calculation, there is an approximate [[Hamiltonian (quantum mechanics)|Hamiltonian]] and an approximate expression for the total electron density. DFT methods can be very accurate for little computational cost. The drawback is that, unlike ab initio methods, there is no systematic way to improve the methods by improving the form of the functional. Some methods combine the density functional exchange functional with the Hartree-Fock exchange term and are known as [[hybrid functional]] methods. === Semi-empirical and empirical methods === {{main|Semi-empirical quantum chemistry methods}} Semi-empirical [[quantum chemistry]] methods are based on the [[Hartree-Fock]] formalism, but make many approximations and obtain some parameters from empirical data. They are very important in computational chemistry for treating large molecules where the full Hartree-Fock method without the approximations is too expensive. The use of empirical parameters appears to allow some inclusion of correlation effects into the methods. Semi-empirical methods follow what are often called empirical methods, where the two-electron part of the [[Hamiltonian (quantum mechanics)|Hamiltonian]] is not explicitly included. For π-electron systems, this was the [[Huckel method|Hückel method]] proposed by [[Erich Hückel]], and for all valence electron systems, the [[Extended Huckel method|Extended Hückel method]] proposed by [[Roald Hoffmann]]. === Molecular mechanics === {{main|Molecular mechanics}} In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. [[Molecular mechanics]] simulations, for example, use a single classical expression for the energy of a compound, for instance the [[harmonic oscillator]]. All constants appearing in the equations must be obtained beforehand from experimental data or ''ab initio'' calculations. The database of compounds used for parameterization, i.e., the resulting set of parameters and functions is called the [[Force field (chemistry)|force field]], is crucial to the success of molecular mechanics calculations. A force field parameterized against a specific class of molecules, for instance proteins, would be expected to only have any relevance when describing other molecules of the same class. These methods can be applied to proteins and other large biological molecules, and allow studies of the approach and interaction (docking) of potential drug molecules (eg. [http://www.bio-balance.com/JMGM_article.pdf] and [http://www.bio-balance.com/GPCR_Activation.pdf]). === Methods for solids === {{main|Computational chemical methods in solid state physics}} Computational chemical methods can be applied to [[solid state physics]] problems. The electronic structure of a crystal is in general described by a [[band structure]], which defines the energies of electron orbitals for each point in the [[Brillouin zone]]. Ab initio and semi-empirical calculations yield orbital energies, therefore they can be applied to band structure calculations. Since it is time-consuming to calculate the energy for a molecule, it is even more time-consuming to calculate them for the entire list of points in the Brillouin zone. === Chemical dynamics === Once the electronic and [[molecular geometry|nuclear]] variables are [[separation of variables|separated]] (within the Born-Oppenheimer representation), in the time-dependent approach, the [[wave packet]] corresponding to the nuclear [[degrees of freedom (physics and chemistry)|degrees of freedom]] is propagated via the [[time evolution]] [[operator (physics)]] associated to the time-dependent [[Schrödinger equation]] (for the full [[molecular Hamiltonian]]). In the [[complementarity (physics)|complementary]] energy-dependent approach, the time-independent [[Schrödinger equation]] is solved using the [[scattering theory]] formalism. The potential representing the interatomic interaction is given by the [[potential energy surface]]s. In general, the [[potential energy surface]]s are coupled via the [[vibronic coupling]] terms. The most popular methods for propagating the [[wave packet]] associated to the [[molecular geometry]] are * the [[split operator technique]], * the [[Multi-Configuration Time-Dependent Hartree]] method (MCTDH), * the [[semiclassical]] method. [[Molecular dynamics]] (MD) examines (using [[Newton's laws of motion]]) the time-dependent behavior of systems, including vibrations or Brownian motion, using a classical mechanical description. MD combined with [[density functional theory]] leads to the [[Car-Parrinello method]]. == Interpreting molecular wave functions == The [[Atoms in Molecules]] model developed by [[Richard Bader]] was developed in order to effectively link the quantum mechanical picture of a molecule, as an electronic wavefunction, to chemically useful older models such as the theory of [[Lewis pair]]s and the [[Valence bond theory|valence bond model]]. Bader has demonstrated that these empirically useful models are connected with the [[topology]] of the quantum charge density. This method improves on the use of [[Mulliken population analysis]]. == Software packages == There are many self-sufficient [[:Category:Computational chemistry software|software packages]] used by computational chemists. Some include many methods covering a wide range, while others concentrating on a very specific range or even a single method. Details of most of them can be found in: * [[Quantum chemistry computer programs]] supporting several methods. * [[Density functional theory#Software supporting DFT|Density functional theory]] programs. * [[Software for molecular mechanics modeling|Molecular mechanics]] programs. * [[Semi-empirical quantum chemistry methods|Semi-empirical]] programs. * [[Computational chemical methods in solid state physics|Solid state system]] programs with periodic boundary conditions. * [[Valence bond codes|Valence Bond]] programs. == See also == <div class="references-small" style="-moz-column-count:3; column-count:3;"> * [[Molecule]] * [[Basis set (chemistry)]] * [[Bioinformatics]] * [[Cheminformatics]] * [[Computational Chemistry List]] * [[List of important publications in chemistry#Computational chemistry|Important publications in computational chemistry]] * [[International Academy of Quantum Molecular Science]] * [[Molecular modelling|Molecular modeling]] * [[Monte Carlo molecular modeling]] * [[Quantum chemistry]] * [[Scientific computing|Computational Science]] * [[Statistical mechanics]] <!-- * [[Potential Distribution Theorem]] comment out until not redlink --> </div> == Cited References == <references/> == Other references == *Christopher J. Cramer ''Essentials of Computational Chemistry'', John Wiley & Sons (2002) *T. Clark ''A Handbook of Computational Chemistry'', Wiley, New York (1985) *R. Dronskowski ''Computational Chemistry of Solid State Materials'', Wiley-VCH (2005) *F. Jensen ''Introduction to Computational Chemistry'', John Wiley & Sons (1999) *D. Rogers ''Computational Chemistry Using the PC, 3rd Edition'', John Wiley & Sons (2003) *Paul von Ragué Schleyer (Editor-in-Chief). ''[http://eu.wiley.com/WileyCDA/WileyTitle/productCd-047196588X.html Encyclopedia of Computational Chemistry]''. Wiley, '''1998'''. ISBN 0-471-96588-X. *A. Szabo, N.S. Ostlund, ''Modern Quantum Chemistry'', McGraw-Hill (1982) *D. Young ''Computational Chemistry: A Practical Guide for Applying Techniques to Real World Problems'', John Wiley & Sons (2001) *David Young's [http://www.ccl.net/cca/documents/dyoung/topics-orig/compchem.html Introduction to Computational Chemistry] == External links == *[http://srdata.nist.gov/cccbdb/ NIST Computational Chemistry Comparison and Benchmark DataBase] - Contains a database of thousands of computational and experimental results for hundreds of systems *[http://www.compchemwiki.org/index.php?title=Main_Page Computational Chemistry Wiki] - Wiki of computational chemistry results *[http://books.nap.edu/openbook.php?record_id=2206&page=R1 CSTB report] Mathematical Research in Materials Science: Opportunities and Perspectives - CSTB Report *[http://ocw.mit.edu/OcwWeb/Materials-Science-and-Engineering/3-320Spring-2005/CourseHome/ 3.320 Atomistic Computer Modeling of Materials (SMA 5107)] Free MIT Course *[http://www.chemicalvision2020.org/pdfs/compchem.pdf Technology Roadmap for Computational Chemistry] *[http://www.wtec.org/molmodel/mm_final.pdf APPLICATIONS OF MOLECULAR AND MATERIALS MODELING.] *[http://books.nap.edu/openbook.php?record_id=9591&page=1 Impact of Advances in Computing and Communications Technologies on Chemical Science and Technology CSTB Report] [[Category:Computational chemistry|Computational chemistry]] [[Category:Theoretical chemistry]] [[Category:Computational science]] [[ar:كيمياء حاسوبية]] [[ca:Química computacional]] [[cs:Výpočetní chemie]] [[de:Computerchemie]] [[es:Química computacional]] [[fr:Chimie numérique]] [[id:Kimia komputasi]] [[it:Chimica computazionale]] [[he:כימיה חישובית]] [[hu:Kémiai számítástechnika]] [[nl:Computationele chemie]] [[ja:計算化学]] [[pl:Chemia obliczeniowa]] [[th:เคมีการคำนวณ]] [[vi:Hóa học tính toán]] [[zh:计算化学]]