I am taking numerical derivatives (acknowledging that it's not generally
the best idea), and the data exhibits some peaks that look spurious. When
I try to resolve them the errors in the values for the ground state energy
become significant. My idea was that if I could control the accuracy of
the ground state energy values I could determine whether the peaks are
indeed there.

Related to the 10 digits of accuracy, the error becomes very noticeable in
the second derivative of the data already for a step size of 0.001.

Best,
Eoin

> sparsediag should always give you at least 10 digits of accuracy. What
> inaccuracy are you talking about?
>
>
>
> On 12 Jun 2014, at 00:09, epquinn@pks.mpg.de wrote:
>
>> Thanks for the response. Two or three decimal places more should be
>> enough
>> to allow me clearly see the features I am looking at. The problem is
>> that
>> at the moment the inaccuracy is washing them out.
>>
>>> What accuracy are you aiming for?
>>>
>>>
>>>
>>>
>>>> On Jun 11, 2014, at 6:42, epquinn@pks.mpg.de wrote:
>>>>
>>>> Greetings,
>>>>
>>>> I am wondering if it is possible to increase the accuracy of
>>>> sparsediag,
>>>> for example for the result it gives for the lowest eigenvalue. There
>>>> does
>>>> not appear to be a suitable input parameter. My understanding is that
>>>> increasing accuracy comes at a computational cost, and I need to tweak
>>>> the
>>>> balance further to the side of accuracy.
>>>>
>>>> With best regards,
>>>> Eoin
>>>>
>>>
>>
>>
>
>