Re: [gmx-users] Long range Lennard Jones

2013-09-02 Thread Szilárd Páll
On Thu, Aug 29, 2013 at 7:18 AM, Gianluca Interlandi wrote: > Justin, > > I respect your opinion on this. However, in the paper indicated below by BR > Brooks they used a cutoff of 10 A on LJ when testing IPS in CHARMM: > > Title: Pressure-based long-range correction for Lennard-Jones interactions

Re: [gmx-users] Long range Lennard Jones

2013-08-30 Thread Justin Lemkul
On 8/29/13 6:23 PM, Gianluca Interlandi wrote: And interestingly, they point out at differences between the various implementations of the switching function. Also, when trying to replicate the CHARMM energies, the authors did not use any cutoff at all and performed the calculations in vacuo. I

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Gianluca Interlandi
And interestingly, they point out at differences between the various implementations of the switching function. Also, when trying to replicate the CHARMM energies, the authors did not use any cutoff at all and performed the calculations in vacuo. If you look at Table 1 in the paper, it is exact

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Gianluca Interlandi
Yes, I've seen that thread before. My feeling is that simulating membranes with the CHARMM36 FF is a different story. It's good to be aware of that. Gianluca On Thu, 29 Aug 2013, Justin Lemkul wrote: On 8/29/13 5:15 PM, Gianluca Interlandi wrote: Of course, if accuracy is not in question th

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Justin Lemkul
On 8/29/13 5:33 PM, Gianluca Interlandi wrote: And also, gromacs does not seem to use the same switching function as CHARMM. Has it been tested how much this affects replication of the original CHARMM MM energies? Yes. dx.doi.org/10.1021/ct900549r -Justin -- ==

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Gianluca Interlandi
And also, gromacs does not seem to use the same switching function as CHARMM. Has it been tested how much this affects replication of the original CHARMM MM energies? Gianluca On Thu, 29 Aug 2013, Gianluca Interlandi wrote: Of course, if accuracy is not in question then performance dominates.

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Justin Lemkul
On 8/29/13 5:15 PM, Gianluca Interlandi wrote: Of course, if accuracy is not in question then performance dominates. I have seen countless reports on this list and elsewhere where small changes in cutoffs lead to wildly incorrect behavior, affecting every force field. Thus, I am always extreme

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Gianluca Interlandi
Of course, if accuracy is not in question then performance dominates. I have seen countless reports on this list and elsewhere where small changes in cutoffs lead to wildly incorrect behavior, affecting every force field. Thus, I am always extremely skeptical of such changes. The effects can b

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Justin Lemkul
On 8/29/13 2:52 PM, Gianluca Interlandi wrote: That's good to know that you've tested different setups. Are the water interaction energies comparable? Have you tested model compounds or just full proteins? Over how long of a time period? I have tested only full proteins over a 50-ns period

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Gianluca Interlandi
That's good to know that you've tested different setups. Are the water interaction energies comparable? Have you tested model compounds or just full proteins? Over how long of a time period? I have tested only full proteins over a 50-ns period. I have not calculated yet the water interactio

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Michael Shirts
IPS in CHARMM involves additional calculations beyond a simple homogeneous approximation -- roughly equivalent to PME for dispersion, though its a bit messier. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2723858/ On Thu, Aug 29, 2013 at 7:56 AM, Justin Lemkul wrote: > > > On 8/29/13 1:18 AM, G

Re: [gmx-users] Long range Lennard Jones

2013-08-29 Thread Justin Lemkul
On 8/29/13 1:18 AM, Gianluca Interlandi wrote: Justin, I respect your opinion on this. However, in the paper indicated below by BR Brooks they used a cutoff of 10 A on LJ when testing IPS in CHARMM: Title: Pressure-based long-range correction for Lennard-Jones interactions in molecular dynami

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Gianluca Interlandi
Justin, I respect your opinion on this. However, in the paper indicated below by BR Brooks they used a cutoff of 10 A on LJ when testing IPS in CHARMM: Title: Pressure-based long-range correction for Lennard-Jones interactions in molecular dynamics simulations: Application to alkanes and inte

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Justin Lemkul
On 8/28/13 9:09 PM, Gianluca Interlandi wrote: Current CHARMM development relies on a 1.2-nm cutoff for LJ, so that's how we balance all of the forces during parameterization. Ok, I agree. What about the use of PME for Coulomb? The CHARMM PARAM22 force field was parametrized using SHIFT on el

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Gianluca Interlandi
Current CHARMM development relies on a 1.2-nm cutoff for LJ, so that's how we balance all of the forces during parameterization. Ok, I agree. What about the use of PME for Coulomb? The CHARMM PARAM22 force field was parametrized using SHIFT on electrostatic forces making it zero after 12 A (pl

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Justin Lemkul
On 8/28/13 7:28 PM, Gianluca Interlandi wrote: Thanks for your replies, Mark. What do you think about the current DispCorr option in gromacs? Is it worth it trying it? Also, I wonder whether using DispCorr for LJ + PME for Cb justifies reducing the cutoff for non-bonded to 1 nm with the CHARMM

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Gianluca Interlandi
Thanks for your replies, Mark. What do you think about the current DispCorr option in gromacs? Is it worth it trying it? Also, I wonder whether using DispCorr for LJ + PME for Cb justifies reducing the cutoff for non-bonded to 1 nm with the CHARMM force field, where 1.2 nm is usually recommende

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Mark Abraham
Secondarily, one could use the same cut-off for LJ and electrostatics, and treat their respective lattice components however you like. This simplifies implementations for computing short-ranged interactions, while facilitating iso-accuracy load balancing across heterogeneous compute units. Mark O

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread David van der Spoel
On 2013-08-28 09:31, rajat desikan wrote: Hi, What is LJ PME? I googled it and got this publication? http://pubs.acs.org/doi/abs/10.1021/ct400146w So, LJ will not be cut off at some r, but you will have a real+fourier part similar to electrostatics. Is that LJ PME? What are the advantages? htt

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread rajat desikan
Hi, What is LJ PME? I googled it and got this publication? http://pubs.acs.org/doi/abs/10.1021/ct400146w So, LJ will not be cut off at some r, but you will have a real+fourier part similar to electrostatics. Is that LJ PME? What are the advantages? On Wed, Aug 28, 2013 at 12:36 PM, Mark Abraham

Re: [gmx-users] Long range Lennard Jones

2013-08-28 Thread Mark Abraham
Lennard-Jones PME is planned for 5.0 Mark On Aug 28, 2013 8:36 AM, "Gianluca Interlandi" wrote: > Hi! > > Just wondering whether gromacs has (or plans to implement) a correction > for the loss of long range LJ interactons? Something similar to > LJcorrection in NAMD or IPS in CHARMM. > > Thanks!

RE: [gmx-users] Long range Lennard Jones

2013-08-27 Thread Dallas Warren
DispCorr might be what you are looking for, correction for LJ beyond the cut-off. Catch ya, Dr. Dallas Warren Drug Discovery Biology Monash Institute of Pharmaceutical Sciences, Monash University 381 Royal Parade, Parkville VIC 3052 dallas.war...@monash.edu +61 3 9903 9304 --