VMD-L Mailing List

From: Leonor Cruzeiro (lhansson_at_ualg.pt)
Date: Mon Feb 05 2007 - 14:04:09 CST

Hello,

I have one comment. Dipole moments are obtaining by multiplying a charge by
a distance and so its units cannot be charge per angstrom, but only charge x
angstrom. In SI, the unit of the dipole moment is coulomb meter. 1 debye =
3.335641 x 10^{-30} Cm. The elementary charge is 1.602177 x 10^{-19}C and 1
m = 10^{10} A, so we have 1 D = 0.20819 e A, or, 1 e A = 4.8 032 D, a factor
very close to the value mentioned by Axel.

Leonor.

----- Original Message -----
From: "John Stone" <johns_at_ks.uiuc.edu>
To: "Axel Kohlmeyer" <akohlmey_at_cmm.chem.upenn.edu>
Cc: "Kim Gunnerson" <gunnek_at_u.washington.edu>; <vmd-l_at_ks.uiuc.edu>
Sent: Monday, February 05, 2007 4:32 PM
Subject: Re: vmd-l: Units for Measure Dipole

>
> Hi,
> In order to make this simpler going forward,
> I'm adding "-elementary" and "-debye" flags to the "measure diple"
> command so you can get the units you want. Without changing the required
> syntax, the defualt would have to remain remain elementary
> charges/Angstrom
> since there are scripts in the field using/assuming that behavior.
> Comments/suggestions welcome.
>
> John Stone
> vmd_at_ks.uiuc.edu
>
> On Fri, Feb 02, 2007 at 07:28:15PM -0500, Axel Kohlmeyer wrote:
>> On Fri, 2 Feb 2007, Kim Gunnerson wrote:
>>
>> KG> Hi,
>> KG>
>>
>> KG> When I use the measure dipole $sel command I get what appears to be
>> KG> a vector. What are the units for the vector?
>>
>> elementary charge per angstrom, if i remember correctly.
>>
>> to convert to Debye you need to multiply with 4.77350732929
>>
>> axel.
>>
>>
>> KG>
>> KG> Thanks
>> KG>
>> KG> Kim Gunnerson
>> KG> Department of Chemistry
>> KG> University of Washington
>> KG>
>>
>> --
>> =======================================================================
>> Axel Kohlmeyer akohlmey_at_cmm.chem.upenn.edu http://www.cmm.upenn.edu
>> Center for Molecular Modeling -- University of Pennsylvania
>> Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
>> tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425
>> =======================================================================
>> If you make something idiot-proof, the universe creates a better idiot.
>
> --
> NIH Resource for Macromolecular Modeling and Bioinformatics
> Beckman Institute for Advanced Science and Technology
> University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
> Email: johns_at_ks.uiuc.edu Phone: 217-244-3349
> WWW: http://www.ks.uiuc.edu/~johns/ Fax: 217-244-6078
>