ONETEPDATASHEETOVERVIEW
Researchers in chemistry, pharmaceuticals, and materials
science may be faced with a number of challenging goals,
such as the development of new compounds or the discovery
of improved manufacturing processes. As researchers treat
more sophisticated problems, such as those in the realmof nanotechnology, they need to employ larger molecularmodels and perform calculations that provide the accuracy andreliability of quantum mechanical approaches.
In the past, this has presented a conundrum because large
models were too computationally expensive to study with firstprinciples methods. As a result, the limitations of hardware
and software forced researchers to make a give-andtake
decision—either use an unrealistically small model in order toobtain quantum mechanical results, or keep a realistic model
but perform only an approximate calculation.
Today, it is no longer necessary to make such compromises
because ONETEP delivers quantum mechanical accuracy forlarge systems.
ONETEP is a linear scaling method, meaning the time required
for a calculation increases linearly with the number of atoms.
As a result of this unique scaling, the program can be used tomodel systems larger than possible in the past.
Typical applications of first-principles quantum mechanics
calculations with ONETEP include studies of:• surface chemistry• structural properties of large molecular systems• energies of protein-ligand complexes• structure and energetics of nanotubes• properties of defects (e.g. vacancies, interstitials,substitution impurities, grain boundaries, and dislocations)in semiconductors and ceramic materials

THE ONETEP ADVANTAGE — LINEAR SCALING
As illustrated by the example shown in Figure 1, the main
advantage of ONETEP is its linear scaling behavior, whichmeans that the time required for calculating the total energy
increases linearly with the number of atoms. This linear
scaling approach is a vast improvement over conventional DFT
methods, where the time needed for computation increases ata rate of as much as N3 (where N is the total number of atoms).
ONETEP also runs very efficiently on multiprocessor computers,
scaling to hundreds of processors. Consequently, with theONETEP module in BIOVIA Materials Studio, it is feasible toperform DFT calculations on very large systems (even oneswith thousands of atoms).

Figure 1: ONETEP linear scaling behavior for the calculation ofthe total energy for a polyethylene oxide (PEO) polymer chain.
Calculation run on 16 dual-core Opteron 2.8 GHz processors, 1
MB cache, 8 GB per processor.

KEY USES OF ONETEP
Insulators, Semiconductors, Glass, and Zeolites
ONETEP takes advantage of the localization of electron density
and, as a consequence, finds its main application in thesimulation of insulators or semiconductors. Amorphous glass
surfaces and zeolites that require large unit cells to be properlydescribed are also well-suited for ONETEP.

Catalysis
Another application for ONETEP is in the area of catalysis,
where it can be used to study the influence of the support
on catalytic activity. To model a support together with anactive nanocluster requires hundreds or even thousands ofatoms. Therefore, a linear scaling DFT code such as ONETEP isessential if one wants to include quantum mechanical effects
in the calculation.

Nanotechnology
ONETEP opens up new possibilities in modeling nanotechnology.
It can be used, for example, to study the electronic structure ofcarbon nanotubes for sensor applications. In particular, it canbe applied to the development of biosensors, which are usuallycomposed of a metal nanowire with antibodies attached
to it. Those antibodies are selective towards a particular
protein. Understanding the reactivity of the proteins requires aquantum mechanical based method, and a linear scaling codeis needed due to the sheer size of the system.

ONETEP can also provide fundamental insight into theelectronic structure of materials that have important industrial
applications. For example, as illustrated by the example ofsilicon supercells shown in Figure 2, ONETEP can model
defects, fracturing and dopants. A better understanding of
the properties of those materials can be translated to better
performance of the final product. Modeling of this type,
together with experiment, has been demonstrated to yield
results at a lower cost than from experiments alone.

• Single-point energy calculation• Geometry optimization• Transition-state search
Each of these calculations can be set up so that it generates
specified chemical and physical properties; specifically:• Electron density• Electrostatic potential• Mulliken charges• Mulliken spins• Bond populations• Density of states (DOS)• Molecular orbitals (MOs)

THE BIOVIA MATERIALS STUDIO ADVANTAGE—TOOLS TO COMPLEMENT ONETEPONETEP is part of the comprehensive BIOVIA Materials Studiomodeling and simulation software environment. BIOVIA
Materials Studio provides a user-friendly interface that complies
with Windows® standards, which together with a varietyof training options, makes it easy for any user to learn thesoftware and apply it with confidence. On top of this, BIOVIA
Materials Studio offers a wealth of modeling and simulation
tools that can be used to supplement ONETEP.
Figure 2: Highest Occupied Molecular Orbital (right) andLowest Unoccupied Molecular Orbital (left) of a siliconsupercell containing 1000 atoms. The ability to study
such large structures is important for modeling defects,
fracturing, and dopants at low concentrations.

HOW DOES ONETEP WORK?
ONETEP implements DFT using the density matrix formulation.
The density matrix is a quantity that is exponentially localized ininsulators and its diagonal elements are equal to the electroniccharge density. Because the elements of the density matrix
are spatially localized, the program performs many fewer
calculations compared to a conventional DFT program in which
the molecular orbitals are delocalized across the entire molecule.
In ONETEP, the density matrix is expressed in terms of a basis
set of localized functions called non-orthogonal generalized
Wannier functions (NGWFs). This provides two advantages.
First, the number of NGWFs can be easily increased to provide
an accurate and complete basis set; second, the NGWFs can belocalized extremely well, reducing the computational effort asmuch as possible. The linear scaling is a direct consequence ofthe localization of NGWFs.

WHAT CALCULATIONS CAN ONETEP PERFORM?
The ONETEP module in BIOVIA Materials Studio allows the user
to perform first-principles quantum mechanical calculations onlarge systems using DFT. ONETEP can currently perform threedifferent tasks:

For example, BIOVIA Materials Visualizer — the core of BIOVIA
Materials Studio — offers a wide range of model building andvisualization tools that allow users to construct models of thesystems of interest. In particular, researchers in nanotechnology
will benefit from the nanotube builder which can create single
walled, multi-walled and bundles of nanotubes, as well as thenanocluster builder, which can create spheres, tetrahedra, andother shapes. From BIOVIA Materials Visualizer, users can theneasily select ONETEP to run an advanced quantum mechanics
calculation.
BIOVIA Materials Studio also offers analysis tools thatcomplement ONETEP. For example, population analysis control
allows the user to assign charges, spins, and bond orders
derived from a Mulliken analysis to the final structure obtainedin a ONETEP calculation, while other tools allow you to display
3D renderings of molecular orbitals.
On top of this, a flexible client-server architecture means thatcalculations can be run on servers located anywhere on acompany’s network. Results are returned to a user’s PC, where
they may be displayed and analyzed. It is easy to produce
high quality graphics of molecular and materials structures, aswell as molecular orbitals. Structures, graphs and other data,such as video clips, can be instantly exchanged with other PCapplications, facilitating sharing among colleagues and analysis
in spreadsheets or other packages.
To learn more about BIOVIA Materials Studio, go toaccelrys.com/materials-studioOur 3DEXPERIENCE Platform powers our brand applications, serving 12 industries, and provides a richportfolio of industry solution experiences.
Dassault Systèmes, the 3DEXPERIENCE Company, provides business and people with virtual universes to imagine sustainable innovations. Its world-leadingsolutions transform the way products are designed, produced, and supported. Dassault Systèmes’ collaborative solutions foster social innovation, expanding
possibilities for the virtual world to improve the real world. The group brings value to over 170,000 customers of all sizes in all industries in more than 140
countries. For more information, visit www.3ds.com.

Dassault Systèmes Corporate
Dassault Systèmes
175 Wyman StreetWaltham, Massachusetts
02451-1223
USA

BIOVIA Corporate Americas
BIOVIA
5005 Wateridge Vista Drive,
San Diego, CA92121
USA

BIOVIA Corporate Europe
BIOVIA
334 Cambridge Science Park,Cambridge CB4 0WN
England

DS-8014-1014©2014 Dassault Systèmes. All rights reserved. 3DEXPERIENCE, the Compass icon and the 3DS logo, CATIA, SOLIDWORKS, ENOVIA, DELMIA, SIMULIA, GEOVIA, EXALEAD, 3D VIA, BIOVIA and NETVIBES are commercial trademarks
or registered trademarks of Dassault Systèmes or its subsidiaries in the U.S. and/or other countries. All other trademarks are owned by their respective owners. Use of any Dassault Systèmes or its subsidiaries trademarks is subject to their express written approval.

Industrial Materials