Last update: 14 June 2015
 Introduction
 What is deMon?
 Who are the deMon developers?
 deMonDynaRho: The original deMon TDDFT program
 Who are we?
 deMon@Grenoble: Our integration of TDDFT into deMon2k
 Want to try it out?
The following web page is intended as an introduction to Grenoble efforts within the deMon development community and, by extension, within the greater community of developers of software for theoretical and computational chemistry. The name "Casida" is wellknown among quantum chemists and theoretical solid state physicists for pioneering efforts in timedependent densityfunctional theory (TDDFT.) Not surprisingly most of the Grenoble contribution to deMon development is related to TDDFT.
In order to understand the notion of the deMon development community, it is first important to have some basic notions about the deMon family of programs. These points are covered in the next two sections.
The Grenoble development version of deMon is not intended to be a separate branch of deMon but rather to be a place to develop ideas that will eventually find their place in deMon2k. Our development effort focuses primarily on improving TDDFT in future releases of deMon2k. Nevertheless logially we are a little ahead of the deMon2k master version in our efforts. To understand our development version deMon@Grenoble, it is best to first know a bit about its predecessor deMonDynaRho, which was one of the first (if not the first) implementation of TDDFT in a Quantum Chemistry program. That program was used as a separate postdeMonKS program, making it unsuitable as a starting point for excitedstate geometry optimizations. This, and the superiority of the deMon2k integral package over the deMonKS integral package, was at the origin of the decision to abandon further development of deMonDynaRho. Instead we chose to focus our efforts on implementing an improved version of TDDFT within the deMon2k code.
We welcome inquiries about trying out deMon2k and deMon@Grenoble. Please see below.
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deMon is short for densité de Montréal ("density of Montreal.") It is a family of programs which grew out of Alain StAmant's PhD thesis with Dennis R. Salahub at the Université de Montréal (UdM) in Montreal, Quebec, Canada. The main deMon program of that period came to be known as deMonKS.
Beginning around 1995, the master deMon program began to be rewritten from the bottom up. The principal author of the current master version of deMon, known as deMon2k, is Andreas Köster. The official citation for that version is,
 deMon2k, Andreas M. Köster, Patrizia Calaminici, Mark E. Casida, Roberto FloresMoreno, Gerald Geudtner, Annick Goursot, Thomas Heine, Andrei Ipatov, Florian Janetzko, Jorge M. del Campo, Serguei Patchkovskii, J. Ulises Reveles, Dennis R. Salahub, Alberto Vela, The International deMon Developers Community (CinvestavIPN, Mexico, 2006).
Gerald Geudtner is currently responsible for gathering updates from deMon developers and putting them in this master version. See an old version of the deMon2k manual (PDF)
However there are several associated programs and evolutionary spinoffs of deMon2k and of the earlier deMonKS. Once such is the StockholmBerlin (StoBe) version of deMonKS. Another is the deMon2K_KSCED spinoff of deMon2K developed in Geneva which allows for two types of beyondKohnSham methods:
 orbitalfree embedding calculations following WesolowskiWarshel embedding formalism, and
 fully variational calculations following Cortona formulation of density functional theory.
The present page concerns a local development version of deMon2k which we call deMon@Grenoble. An important predecessor of deMon@Grenoble was deMonDynaRho.
It is a bit hard to define what exactly makes deMon so special. Is it the people who haved worked on it over the years? The innovative things we have done with the program which have since spread to other quantum chemistry and physics programs? Suffice it to say that most deMon programs are characterized by the use of a double basis set. The molecular orbitals are expanded in an orbital basis set consisting of atomic orbitals represented as contractions of Gaussiantype orbitals,
ψ_{i}(r) = Σ_{μ} χ_{μ}(r) c_{μ,i} .
The density,
ρ(r) = Σ_{i} ψ_{i}(r) n_i Σ_{i} ψ_{i}(r) = Σ_{μ,ν} χ_{μ}(r) (Σ_{i}^{occ} c_{μ,i} c_{ν,i}) χ_{ν}(r) = Σ_{μ,ν} χ_{μ}(r) P_{μ,ν} χ_{ν}(r) ,
is approximated by an expansion in an auxiliary basis set,
ρ'(r) = Σ_{I} f_{I}(r) a_{I} ,
where the fitting coefficients are obtained by minimizing the electron repulsion "error" integral,
 Δ ρ^{2} = [ρρ'  1/r_{12}  ρρ'] .
This auxiliary basis allows all 4center electron repulsion integrals to be eliminated from deMon, thus permitting a formal O(N^{3}) scaling, instead of the usual formal O(N^{3}) (or worse) scaling of normal ab initio quantum chemistry programs. In practice scaling can be significantly better than O(N^{3}) because of additional tricks of the trade. Another program with a similar philosphy was DGauss, developped at Cray Inc. Of course, there is much more to deMon programs than just auxiliary basis sets, but that and analytic derivatives for geometry optimizations was a key historical starting point for deMon.
Additional information about deMon may be found below and also at http://www.demonsoftware.com/public_html/index.html.
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Many, but by no means all of the deMon developers, were at some time associated with the Salahub group at UdM. In fact the deMon logo,
,
is intended to look a bit like the main building on that university campus,
.
Since then the deMon developers have all left UdM and spread around the world. deMon developers meetings are hosted annually by developers around the world. Here is a list of previous meetings:
Workshop 
Year 
Place 
1st 
1419 March 2000 
Steacie Institute (Ottawa, Ontario, Canada) 
2nd 
1216 March 2001 
CINVESTAV (Mexico City, Mexico) 
3rd 
26 April 2002 
Université de Genève (Geneva, Switzerland) 
4th 
2226 April 2003 
Stockholms Universitet (Stockholm, Sweden) 
5th 
15 May 2004 
Tropea, Italy (hosted by the University of Calabria) 
6th 
30 March  3 April 2005 
Techninische Universität Dresden, Dresden, Germany 
7th 
2125 April 2006 
Kananaskis Field Station, Kananaskis Country, Alberta, Canada 
8th 
31 August3 September 2007 
Université René Descartes (Paris V), Paris, France 
9th 
1619 February 2009 
National Chemistry Laboratory, Pune, India 
10th 
1718 May 2010

Universidade Federal de Minas Gerais, Belo Horizone, Brazil

11th  13 July 2011
 Jacobs University, Bremen, Germany
 12th
   13th    14th    15th
  
This helps us to coordinate deMon development but we have still found it useful for deMon developers to have their own versions designed to meet local research objectives, and also to provide a testing ground for new ideas before they go into the master version. deMon@Grenoble is just one example.
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The post deMonKS program, deMonDynaRho is the immediate predecessor of Grenoble's contributions to deMon2k. It represents what was probably the first implementation of timedependent densityfunctional theory (TDDFT) in a Quantum Chemistry program. (Notes in French and in Englsih for an introductory course on TDDFT may be found at http://dcm.ujfgrenoble.fr/PERSONNEL/CT/casida/Enseignement/M2/TDDFT/index.html.)
A detailed account of what are sometimes known as "Casida's equations" for linear response theory is,
 [C95b] M.E. Casida, in Recent Advances in Density Functional Methods, Part I, edited by D.P. Chong (Singapore, World Scientific, 1995), p. 155.
"Timedependent densityfunctional response theory for molecules''
postscript preprint
The approach therein described was implemented in deMonDynaRho,
 [CJB+94] M.E. Casida, C. Jamorski, F. Bohr, J. Guan, and D.R. Salahub, in Theoretical and Computational Modeling of NLO and Electronic Materials, edited by S.P. Karna and A.T. Yeates (ACS Press: Washington, D.C., 1996), (Proceedings of ACS Symposium, Washington, D.C., 1994), p. 145.
"Optical Properties from DensityFunctional Theory"
 [JCS96] Christine Jamorski, Mark E. Casida, and Dennis R. Salahub, J. Chem. Phys. 104, 5134 (1996).
"Dynamic Polarizabilities and Excitation Spectra from a Molecular Implementation of TimeDependent DensityFunctional Response Theory: N_{2} as a Case Study"
We used deMonDynaRho to make several contributions to the scientific community. These include a highlycited article [CJCS98] on the artificially low onset of the TDDFT ionization threshold at ε_{HOMO} as well as articles [CCS98,CS00] reporting a simple asymptotic correction scheme to fix the problem,
 [CJCS98] M.E. Casida, C. Jamorski, K.C. Casida, and D.R. Salahub, J. Chem. Phys. 108, 4439 (1998).
"Molecular excitation energies to highlying bound states from timedependent densityfunctional response theory: Characterization and correction of the timedependent local density approximation ionization threshold"
 [CCS98] M.E. Casida, K.C. Casida, and D.R. Salahub, Int. J. Quant. Chem. 70, 933 (1998). (International Journal of Quantum Chemistry, Quantum Chemistry Symposium No. 32, Proceedings of the International Symposium on Atomic, Molecular, and Condensed Matter Theory)
"Excitedstate potential energy curves from timedependent densityfunctional theory: A crosssection of formaldehyde's ^{1}A_{1 }manifold"
PDF file
 [CS00] Mark E. Casida and Dennis Salahub, J. Chem. Phys. 113, 8918 (2000).
"Asymptotic correction approach to improving approximate exchangecorrelation potentials: Timedependent densityfunctional theory calculations of molecular excitation spectra"
Article [CJCS98] is also interesting in so far as it represents the first treatment of an avoided crossing within a DFTbased method.
An attempt was made to reconcile TDDFT with the ΔSCF method which often gives similar results when both are applicable,
 [C99b] M.E. Casida, in the Online Workshop Proceedings of the Joint ITP/INT Workshop on TimeDependent Density Functional Theory,
1517 April 1999, Institute for Theoretical Physics, University of California at Santa Barbara: http://www.itp.ucsb.edu/online/tddft_c99/
"Reconciling of the DeltaSCF and TDDFT Approaches to Excitation Energies in DFT: A ChargeTransfer Correction for TDDFT with GGA Functionals" This subject was later revisited in the context of the charge transfer problem,
 [CGG+00] Mark E. Casida, Fabien Gutierrez, Jingang Guan, FlorentXavier Gadea, Dennis Salahub, and JeanPierre Daudey, J. Chem. Phys. 113, 7062 (2000).
"Chargetransfer correction for improved timedependent local density approximation excitedstate potential energy curves: Analysis within the twolevel model with illustration for H_{2} and LiH"
The spectra of openshell molecules has been investigated,
We also used deMonDynaRho to make some contributions to the problem of DFTbased calculations of NMR chemical shifts,
 [FCS03a] E. Fadda, M.E. Casida, and D.R. Salahub, Int. J. Quant. Chem. 91, 67 (2003).
"TimeDependent DensityFunctional Theory as a Foundation for a Firmer Understanding of SumOverStates DensityFunctionalPerturbation Theory: The 'Loc.3' Approximation"
 [FCS03b] E. Fadda, M.E. Casida, and D.R. Salahub, J. Chem. Phys. 118, 6758 (2003).
"NMR Shieldings from SumOverStates DensityFunctional Theory: Further Testing of the 'Loc.3' Approximation"
 [FCS03] Elisa Fadda, Mark E. Casida, Dennis R. Salahub, J. Phys. Chem. A 107, 9924 (2003).
"^{14,15}N NMR Shielding Constants from DensityFunctional Theory"
In short, we made a significant number of contributions to DFT and TDDFT using deMonDynaRho. The citation of one of the last official versions of this program was,
 deMonDynaRho version 3.1, M.E. Casida, C. Jamorski, J. Guan, S. Hamel, and D.R. Salahub, University of Montreal, 2001.
Click here to see the deMonDynaRho manual. We still keep a copy of deMonDynaRho, but it was never intended to be much more than a prototype "toy" program to investigate fundamental aspects of TDDFT on very simple systems. We learned a lot from this program and it became stable and reliable for calculations on small molecules, but we could not handle even moderately large systems such as pnitroaminobenzene. And the postSCF nature of deMonDynaRho prevented us from implemented excitedstate forces.
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The Casida group as of 7 May 2009 (photo by Anushree KAMATH). From left to right: Miquel HUIX I ROTLLANT (Doctoral student), Mark E. CASIDA, Bhaarathi NATARAJAN (Doctoral student), Sébastien BRUNEAU (Masters student), Loïc JOUBERT DORIOL (Masters student). Far right: C. Muhavini WAWIRE (Doctoral student).
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Around 2001, a decision was made to integrate TDDFT (and other good features) from deMonDynaRho into the master version of deMon2k. We have had some success with this (which is why Andrei Ipatov and Mark E. Casida figure on the author list for deMon2k) in that we can now routinely handle larger molecules than deMonDynaRho ever could. But we still lack many features from deMonKS/ deMonDynaRho which we are gradually putting into our local development version, deMon2k@Grenoble. At the same time, we are using deMon2k@Grenoble to test out new creative ideas. Click here to see the deMon@Grenoble team.
Grenoble developments which may find their way into future versions of deMon2k include:
 Calculation of the expectation value of S^{2} for excited states in TDDFT.
 Noncollinear spinflip TDDFT.
We are also working on
 Improving the block Davidson procedure.
 Analytic derivatives for TDDFT excited states.
 Polarization propagator corrections going beyond the TDDFT adiabatic approximation.
 TDDFT with fractional occupation numbers.
Relevant publications include:
 [IFP+06] Andrei Ipatov, Antony Fouqueau, Carlos Perez del Valle, Felipe Cordova, Mark E. Casida, Andreas M. Köster, Alberto Vela, and Christine Jödicke Jamorski, J. Molec. Struct. (Theochem), 762, 179 (2006).
''Excitation Energies from an AuxiliaryFunction Formulation of TimeDependent DensityFunctional Response Theory with Charge Conservation Constraint''
This article describes our first reimplementation of TDDFT in deMon2k@Grenoble. An important issue was to harmonize the auxiliary function numerical method so as to be able to go on and implement analytical derivatives for excited states.
 [CIC06] M.E. Casida, A. Ipatov, and F. Cordova, in TimeDependent DensityFunctional Theory, edited by M.A.L. Marques, C. Ullrich, F. Nogueira, A. Rubio, and E.K.U. Gross, Lecture Notes in Physics (Springer: Berlin, 2006), pp. 243257.
LinearResponse TimeDependent DensityFunctional Theory for OpenShell Molecules
preprint
This article reports our work on spincontamination for TDDFT excitedstates.
 [CJI+07] Felipe Cordova, L. Joubert Doriol, Andrei Ipatov, Mark E. Casida, Claudia Filippi, and Alberto Vela, arXiv:0708.1381v1 [condmat.other] 10 Aug 2007, J. Chem. Phys. 127, 164111 (2007).
"Troubleshooting TimeDependent DensityFunctional Theory for Photochemical Applications: Oxirane"
The TammDancoff calculations in this paper were done with deMon2k@Grenoble.  [HNI+10] Miquel HuixRotllant, Bhaarathi Natarajan, Andrei Ipatov,
C. Muhavini Wawire, Thierry Deutsch, and Mark E. Casida, Phys. Chem. Chem. Phys.,
12, 1281112825 (2010).
"Assessment of Noncollinear SpinFlip TammDancoff Approximation TimeDependent
DensityFunctional Theory for the Photochemical RingOpening of Oxirane"
This article reports our implementation of testing of the noncollinear spinflip formalism in deMon2k@Grenoble. This article reports our implementation of testing of dressed TDDFT in deMon2k@Grenoble.
Here is a sample of local documentation for our development version:
 EXCITation keyword (HTML)  documentation of changes made by Andrei Ipatov
 NONCOL keyword  documentation of the noncollinear spinflip TDDFT method implemented by Andrei Ipatov
 SYMMETRY keyword  documentation of
the molecular orbital symmetry labeling option implemented by Bhaarathi
Natarajan.
If you are interested in obtaining a copy of deMon2k or of deMon2k@Grenoble, then please see below.
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deMon is not an "opensource" "copy left" program, but it is essentially free to collaborators, who have signed and returned to us our license agreement. (Note however that certain versions of deMon, such as deMonStoBe, do require the payment of a minor sum, which is, for example, used to help defray the fees of deMon developers meetings.) If you are interested in the the master version of deMon2k, click on the logo,
,
or set your web browser to http://www.demonsoftware.com/public_html/index.html.
Here in Grenoble, we also welcome serious collaborations with scientists wanting to help develop, apply, or just test deMon2k@Grenoble. (As of 6 April 2009, we have distributed one copy of the code to external users.) The recommended citation is,
 deMon2k@Grenoble, the Grenoble development version of deMon2k, Andreas M. Köster, Patrizia Calaminici, Mark E. Casida, Roberto FloresMoreno, Gerald Geudtner, Annick Goursot, Thomas Heine, Andrei Ipatov, Florian Janetzko, Jorge M. del Campo, Serguei Patchkovskii, J. Ulises Reveles, Dennis R. Salahub, Alberto Vela, The International deMon Developers Community (CinvestavIPN, Mexico, 2006).
Please contact me at Mark.Casida@ujfgrenoble.fr for further information. If all goes well, you will be asked to sign our license agreement with the mention "Calculations with the deMon2k@Grenoble development version" under the heading "Research Purpose." For a few priveledged few, you may be even allowed into the inner circle of deMon2k@Grenoble developers  those who have access to our private pages by clicking on this picture of the last vestige of Grenoble's legendary city walls ( La porte de France).
,
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Si vous avez rencontré des difficultés avec mes pages www, veuillez me contacter à Mark.Casida@ujfgrenoble.fr.
Should you encounter difficulties with my web pages, please contact me at: Mark.Casida@ujfgrenoble.fr. 
Updating...
Ċ Mark Casida, Nov 5, 2010, 10:35 AM
Ċ Mark Casida, May 12, 2011, 3:53 AM
Ċ Mark Casida, May 12, 2011, 3:53 AM
