Araqchi said the negotiations on Tuesday were long and intensive on three unnamed topics, with a fourth being considered on Wednesday.
The spokesman for the 5+1 Powers, Michael Mann, said the meetings were constructive.
The European Unions Catherine Ashton and Iranian Foreign Minister Mohammad Javad Zarif opened the talks in the morning, with Ashtons deputy Helga Schmid and Araqchi chairing the negotiations in the afternoon.
Araqchi said the meetings were mainly for exchanging views to find common ground before the two sides work on a joint text.
Iran and the 5+1 Powers opened talks on a comprehensive agreement last month in Vienna, following implementation of Novembers interim nuclear deal.
Larijani: Nuclear Talks Must Not Touch on Human Rights in Iran
Senior judiciary official Mohammad Javad Larijani has warned that nuclear talks in Vienna must not touch on human rights in Iran, warning, The enemies ploy is a vicious circle, which changes according to the political situation.
Iranian officials have harshly criticized UN leaders, including Secretary General Ban Ki-Moon, over reports this month that challenged the Islamic Republic over issues such as executions, womens rights, and political prisoners.
Larijani continued the campaign on Tuesday, rejecting the 3,000 accusations of the UN Special Rapporteur on Human Rights in Iran, Ahmed Shaheed, and describing him as a media actor.
The Iranian official, whose brothers are Speaker of Parliament and head of the judiciary, said Tehran would continue to refuse entry to Shaheed, appointed in 2011: His visit to Iran is not meant to be for verification purposes, but it is for propaganda; how does he want to study 3,000 allegations in just three days?
Larijani has previously declared that Ahmed Shaheed supports terrorism extensively.
National Security Council Files Complaint Against MP Over Nuclear Remarks
The Supreme National Security Council has filed a complaint against MP Mahmoud Nabavian over his criticism of the interim nuclear deal.
Nabavian, a prominent critic of the Government, has denounced the nuclear negotiations in speeches at several universities. He responded to the complaint by saying that he and other critics heavily under pressure: It seems (they) do not believe in freedom of speech at all.
Senior Official: We Can Resume Enrichment of 20% Uranium in 2-3 Hours
The spokesman of Irans Atomic Energy Organization has said that, if nuclear talks do not progress, Tehrancan quickly resume enrichment of uranium to 20%.
Behrouz Kamalvand said Iran had suspended the enrichment under Novembers interim nuclear deal to build trust. However, the Islamic Republic could resume in less than a day; two-three hours.
Uranium enriched to 20% cannot be used for military purposes, but it may be further enhanced to more than 90%, which can fuel nuclear weapons.
Under the interim deal, which came into effect on January 20, Iran agreed to dilute its 20% stock to 5% or to convert it to fuel plates.